--- jsr166/src/jsr166e/ForkJoinPool.java 2012/11/19 18:12:28 1.18
+++ jsr166/src/jsr166e/ForkJoinPool.java 2012/12/08 14:08:44 1.26
@@ -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.
*
@@ -99,16 +99,12 @@ 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
-<<<<<<< ForkJoinPool.java
- * exceptionHandler} -- the class name of a {@code
-=======
* exceptionHandler} -- the class name of a {@link
* java.lang.Thread.UncaughtExceptionHandler
->>>>>>> 1.111
* Thread.UncaughtExceptionHandler}. Upon any error in establishing
* these settings, default parameters are used.
*
@@ -320,17 +316,18 @@ public class ForkJoinPool extends Abstra
* execute. However, many other threads may notice the same task
* and each signal to wake up a thread that might take it. So in
* general, pools will be over-signalled. When a submission is
- * added or another worker adds a task to a queue that is
- * apparently empty, they signal waiting workers (or trigger
- * creation of new ones if fewer than the given parallelism
- * level). These primary signals are buttressed by signals
- * whenever other threads scan for work or do not have a task to
- * process (including the case of leaving a hint to unparked
- * threads to help signal others upon wakeup). On most platforms,
- * signalling (unpark) overhead time is noticeably long, and the
- * time between signalling a thread and it actually making
- * progress can be very noticeably long, so it is worth offloading
- * these delays from critical paths as much as possible.
+ * added or another worker adds a task to a queue that has fewer
+ * than two tasks, they signal waiting workers (or trigger
+ * creation of new ones if fewer than the given parallelism level
+ * -- signalWork), and may leave a hint to the unparked worker to
+ * help signal others upon wakeup). These primary signals are
+ * buttressed by others (see method helpSignal) whenever other
+ * threads scan for work or do not have a task to process. On
+ * most platforms, signalling (unpark) overhead time is noticeably
+ * long, and the time between signalling a thread and it actually
+ * making progress can be very noticeably long, so it is worth
+ * offloading these delays from critical paths as much as
+ * possible.
*
* Trimming workers. To release resources after periods of lack of
* use, a worker starting to wait when the pool is quiescent will
@@ -538,6 +535,26 @@ public class ForkJoinPool extends Abstra
}
/**
+ * Per-thread records for threads that submit to pools. Currently
+ * holds only pseudo-random seed / index that is used to choose
+ * submission queues in method externalPush. In the future, this may
+ * also incorporate a means to implement different task rejection
+ * and resubmission policies.
+ *
+ * Seeds for submitters and workers/workQueues work in basically
+ * the same way but are initialized and updated using slightly
+ * different mechanics. Both are initialized using the same
+ * approach as in class ThreadLocal, where successive values are
+ * unlikely to collide with previous values. Seeds are then
+ * randomly modified upon collisions using xorshifts, which
+ * requires a non-zero seed.
+ */
+ static final class Submitter {
+ int seed;
+ Submitter(int s) { seed = s; }
+ }
+
+ /**
* Class for artificial tasks that are used to replace the target
* of local joins if they are removed from an interior queue slot
* in WorkQueue.tryRemoveAndExec. We don't need the proxy to
@@ -603,7 +620,10 @@ public class ForkJoinPool extends Abstra
* trades off slightly slower average field access for the sake of
* avoiding really bad worst-case access. (Until better JVM
* support is in place, this padding is dependent on transient
- * properties of JVM field layout rules.)
+ * properties of JVM field layout rules.) We also take care in
+ * allocating, sizing and resizing the array. Non-shared queue
+ * arrays are initialized by workers before use. Others are
+ * allocated on first use.
*/
static final class WorkQueue {
/**
@@ -626,6 +646,9 @@ public class ForkJoinPool extends Abstra
*/
static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
+ // Heuristic padding to ameliorate unfortunate memory placements
+ volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
+
int seed; // for random scanning; initialize nonzero
volatile int eventCount; // encoded inactivation count; < 0 if inactive
int nextWait; // encoded record of next event waiter
@@ -643,25 +666,46 @@ public class ForkJoinPool extends Abstra
volatile ForkJoinTask> currentJoin; // task being joined in awaitJoin
ForkJoinTask> currentSteal; // current non-local task being executed
- // Heuristic padding to ameliorate unfortunate memory placements
- Object p00, p01, p02, p03, p04, p05, p06, p07;
- Object p08, p09, p0a, p0b, p0c;
+ volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
+ volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
int seed) {
- this.array = new ForkJoinTask>[WorkQueue.INITIAL_QUEUE_CAPACITY];
this.pool = pool;
this.owner = owner;
this.mode = mode;
this.seed = seed;
- // Place indices in the center of array
+ // Place indices in the center of array (that is not yet allocated)
base = top = INITIAL_QUEUE_CAPACITY >>> 1;
}
/**
- * Pushes a task. Call only by owner in unshared queues.
- * Cases needing resizing or rejection are relayed to fullPush
- * (that also handles shared queues).
+ * Returns the approximate number of tasks in the queue.
+ */
+ final int queueSize() {
+ int n = base - top; // non-owner callers must read base first
+ return (n >= 0) ? 0 : -n; // ignore transient negative
+ }
+
+ /**
+ * Provides a more accurate estimate of whether this queue has
+ * any tasks than does queueSize, by checking whether a
+ * near-empty queue has at least one unclaimed task.
+ */
+ final boolean isEmpty() {
+ ForkJoinTask>[] a; int m, s;
+ int n = base - (s = top);
+ return (n >= 0 ||
+ (n == -1 &&
+ ((a = array) == null ||
+ (m = a.length - 1) < 0 ||
+ U.getObject
+ (a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
+ }
+
+ /**
+ * Pushes a task. Call only by owner in unshared queues. (The
+ * shared-queue version is embedded in method externalPush.)
*
* @param task the task. Caller must ensure non-null.
* @throw RejectedExecutionException if array cannot be resized
@@ -670,46 +714,17 @@ public class ForkJoinPool extends Abstra
ForkJoinTask>[] a; ForkJoinPool p;
int s = top, m, n;
if ((a = array) != null) { // ignore if queue removed
- U.putOrderedObject
- (a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
- if ((n = (top = s + 1) - base) <= 1) {
+ int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
+ U.putOrderedObject(a, j, task);
+ if ((n = (top = s + 1) - base) <= 2) {
if ((p = pool) != null)
- p.signalWork(this, 0);
+ p.signalWork(this);
}
else if (n >= m)
growArray();
}
}
- /**
- * Pushes a task if lock is free and array is either big
- * enough or can be resized to be big enough.
- *
- * @param task the task. Caller must ensure non-null.
- * @return true if submitted
- */
- final boolean trySharedPush(ForkJoinTask> task) {
- boolean submitted = false;
- if (qlock == 0 && U.compareAndSwapInt(this, QLOCK, 0, 1)) {
- ForkJoinTask>[] a = array; ForkJoinPool p;
- int s = top;
- try {
- if ((a != null && a.length > s + 1 - base) ||
- (a = growArray()) != null) { // must presize
- int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
- U.putOrderedObject(a, j, task);
- top = s + 1;
- submitted = true;
- }
- } finally {
- qlock = 0; // unlock
- }
- if (submitted && (p = pool) != null)
- p.signalWork(this, 0);
- }
- return submitted;
- }
-
/**
* Initializes or doubles the capacity of array. Call either
* by owner or with lock held -- it is OK for base, but not
@@ -859,21 +874,6 @@ public class ForkJoinPool extends Abstra
return seed = r ^= r << 5;
}
- /**
- * Provides a more accurate estimate of size than (top - base)
- * by ordering reads and checking whether a near-empty queue
- * has at least one unclaimed task.
- */
- final int queueSize() {
- ForkJoinTask>[] a; int k, s, n;
- return ((n = base - (s = top)) < 0 &&
- (n != -1 ||
- ((a = array) != null && (k = a.length) > 0 &&
- U.getObject
- (a, (long)((((k - 1) & (s - 1)) << ASHIFT) + ABASE)) != null))) ?
- -n : 0;
- }
-
// Specialized execution methods
/**
@@ -987,13 +987,14 @@ public class ForkJoinPool extends Abstra
if (t != null) {
(currentSteal = t).doExec();
currentSteal = null;
- ++nsteals;
- if (top != base) { // process remaining local tasks
+ if (base - top < 0) { // process remaining local tasks
if (mode == 0)
popAndExecAll();
else
pollAndExecAll();
}
+ ++nsteals;
+ hint = -1;
}
}
@@ -1070,26 +1071,6 @@ public class ForkJoinPool extends Abstra
defaultForkJoinWorkerThreadFactory;
/**
- * Per-thread records for threads that submit to pools. Currently
- * holds only pseudo-random seed / index that is used to choose
- * submission queues in method externalPush. In the future, this may
- * also incorporate a means to implement different task rejection
- * and resubmission policies.
- *
- * Seeds for submitters and workers/workQueues work in basically
- * the same way but are initialized and updated using slightly
- * different mechanics. Both are initialized using the same
- * approach as in class ThreadLocal, where successive values are
- * unlikely to collide with previous values. Seeds are then
- * randomly modified upon collisions using xorshifts, which
- * requires a non-zero seed.
- */
- static final class Submitter {
- int seed;
- Submitter(int s) { seed = s; }
- }
-
- /**
* Per-thread submission bookkeeping. Shared across all pools
* to reduce ThreadLocal pollution and because random motion
* to avoid contention in one pool is likely to hold for others.
@@ -1099,6 +1080,12 @@ public class ForkJoinPool extends Abstra
static final ThreadLocal submitters;
/**
+ * Permission required for callers of methods that may start or
+ * kill threads.
+ */
+ private static final RuntimePermission modifyThreadPermission;
+
+ /**
* Common (static) pool. Non-null for public use unless a static
* construction exception, but internal usages null-check on use
* to paranoically avoid potential initialization circularities
@@ -1107,12 +1094,6 @@ public class ForkJoinPool extends Abstra
static final ForkJoinPool commonPool;
/**
- * Permission required for callers of methods that may start or
- * kill threads.
- */
- private static final RuntimePermission modifyThreadPermission;
-
- /**
* Common pool parallelism. Must equal commonPool.parallelism.
*/
static final int commonPoolParallelism;
@@ -1148,6 +1129,11 @@ 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; // 20ms
+
+ /**
* 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
@@ -1259,6 +1245,10 @@ public class ForkJoinPool extends Abstra
* declaration order and may differ across JVMs, but the following
* empirically works OK on current JVMs.
*/
+
+ // Heuristic padding to ameliorate unfortunate memory placements
+ volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
+
volatile long stealCount; // collects worker counts
volatile long ctl; // main pool control
volatile int plock; // shutdown status and seqLock
@@ -1269,6 +1259,9 @@ public class ForkJoinPool extends Abstra
final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
final String workerNamePrefix; // to create worker name string
+ 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
@@ -1329,18 +1322,6 @@ public class ForkJoinPool extends Abstra
}
/**
- * Tries to create and start a worker; adjusts counts etc on failure
- */
- private void addWorker() {
- ForkJoinWorkerThread wt = null;
- try {
- (wt = factory.newThread(this)).start();
- } catch (Throwable ex) {
- deregisterWorker(wt, ex); // adjust on failure
- }
- }
-
- /**
* 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
@@ -1349,29 +1330,57 @@ public class ForkJoinPool extends Abstra
* fullExternalPush.) Because the plock seq value can eventually
* wrap around zero, this method harmlessly fails to reinitialize
* if workQueues exists, while still advancing plock.
+ *
+ * Additionally tries to create the first worker.
*/
- private void initWorkQueuesArray() {
- WorkQueue[] ws; int ps;
+ 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;
- WorkQueue[] nws = new WorkQueue[(n + 1) << 1];
+ 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)
+ 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 if fewer than target
+ * parallelism level exist. Adjusts counts etc on failure.
+ */
+ private void tryAddWorker() {
long c; int u;
- if ((u = (int)((c = ctl) >>> 32)) < 0 && (int)c == 0) {
+ while ((u = (int)((c = ctl) >>> 32)) < 0 &&
+ (u & SHORT_SIGN) != 0 && (int)c == 0) {
long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
((u + UAC_UNIT) & UAC_MASK)) << 32;
- if (U.compareAndSwapLong(this, CTL, c, nc))
- addWorker();
+ if (U.compareAndSwapLong(this, CTL, c, nc)) {
+ ForkJoinWorkerThreadFactory fac;
+ Throwable ex = null;
+ ForkJoinWorkerThread wt = null;
+ try {
+ if ((fac = factory) != null &&
+ (wt = fac.newThread(this)) != null) {
+ wt.start();
+ break;
+ }
+ } catch (Throwable e) {
+ ex = e;
+ }
+ deregisterWorker(wt, ex);
+ break;
+ }
}
-
}
// Registering and deregistering workers
@@ -1384,42 +1393,45 @@ public class ForkJoinPool extends Abstra
* expanding as needed.
*
* @param wt the worker thread
+ * @return the worker's queue
*/
- final void registerWorker(ForkJoinWorkerThread wt) {
- if (wt != null && wt.workQueue == null) {
- int s, ps; // generate a rarely colliding candidate index seed
- do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
- s += SEED_INCREMENT) ||
- s == 0); // skip 0
- WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
- try {
- WorkQueue[] ws;
- if ((ws = workQueues) != null && wt.workQueue == null) {
- int n = ws.length, m = n - 1;
- int r = (s << 1) | 1; // use odd-numbered indices
- if (ws[r &= m] != null) { // collision
- int probes = 0; // step by approx half size
- int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
- while (ws[r = (r + step) & m] != null) {
- if (++probes >= n) {
- workQueues = ws = Arrays.copyOf(ws, n <<= 1);
- m = n - 1;
- probes = 0;
- }
+ final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
+ Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
+ wt.setDaemon(true);
+ if ((handler = ueh) != null)
+ wt.setUncaughtExceptionHandler(handler);
+ do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
+ s += SEED_INCREMENT) ||
+ s == 0); // skip 0
+ WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
+ if (((ps = plock) & PL_LOCK) != 0 ||
+ !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
+ ps = acquirePlock();
+ int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
+ try {
+ if ((ws = workQueues) != null) { // skip if shutting down
+ int n = ws.length, m = n - 1;
+ int r = (s << 1) | 1; // use odd-numbered indices
+ if (ws[r &= m] != null) { // collision
+ int probes = 0; // step by approx half size
+ int step = (n <= 4) ? 2 : ((n >>> 1) & EVENMASK) + 2;
+ while (ws[r = (r + step) & m] != null) {
+ if (++probes >= n) {
+ workQueues = ws = Arrays.copyOf(ws, n <<= 1);
+ m = n - 1;
+ probes = 0;
}
}
- w.eventCount = w.poolIndex = r; // volatile write orders
- wt.workQueue = ws[r] = w;
}
- } finally {
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
+ w.eventCount = w.poolIndex = r; // volatile write orders
+ ws[r] = w;
}
+ } finally {
+ if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
+ releasePlock(nps);
}
+ wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
+ return w;
}
/**
@@ -1460,15 +1472,36 @@ public class ForkJoinPool extends Abstra
((c - TC_UNIT) & TC_MASK) |
(c & ~(AC_MASK|TC_MASK)))));
- if (!tryTerminate(false, false) && w != null) {
+ if (!tryTerminate(false, false) && w != null && w.array != null) {
w.cancelAll(); // cancel remaining tasks
- if (w.array != null) // suppress signal if never ran
- helpSignal(null, 0); // wake up or create replacement
- if (ex == null) // help clean refs on way out
- ForkJoinTask.helpExpungeStaleExceptions();
+ int e, u, i, n; WorkQueue[] ws; WorkQueue v; Thread p;
+ while ((u = (int)((c = ctl) >>> 32)) < 0) {
+ if ((e = (int)c) > 0) { // activate or create replacement
+ if ((ws = workQueues) != null &&
+ ws.length > (i = e & SMASK) &&
+ (v = ws[i]) != null && v.eventCount == (e | INT_SIGN)) {
+ long nc = (((long)(v.nextWait & E_MASK)) |
+ ((long)(u + UAC_UNIT) << 32));
+ if (U.compareAndSwapLong(this, CTL, c, nc)) {
+ v.eventCount = (e + E_SEQ) & E_MASK;
+ if ((p = v.parker) != null)
+ U.unpark(p);
+ break;
+ }
+ }
+ else
+ 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);
}
@@ -1490,11 +1523,12 @@ public class ForkJoinPool extends Abstra
U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
int b = q.base, s = q.top, n, an;
if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
- U.putObject(a, (long)(((an - 1) & s) << ASHIFT) + ABASE, task);
+ int j = (((an - 1) & s) << ASHIFT) + ABASE;
+ U.putOrderedObject(a, j, task);
q.top = s + 1; // push on to deque
q.qlock = 0;
if (n <= 2)
- signalWork(q, 0);
+ signalWork(q);
return;
}
q.qlock = 0;
@@ -1506,15 +1540,15 @@ 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
- * initWorkQueuesArray). 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
- * lock body must be exception-free (so no try/finally) so we
+ * 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.
*/
private void fullExternalPush(ForkJoinTask> task) {
- int r = 0;
+ int r = 0; // random index seed
for (Submitter z = submitters.get();;) {
WorkQueue[] ws; WorkQueue q; int ps, m, k;
if (z == null) {
@@ -1532,12 +1566,29 @@ public class ForkJoinPool extends Abstra
throw new RejectedExecutionException();
else if (ps == 0 || (ws = workQueues) == null ||
(m = ws.length - 1) < 0)
- initWorkQueuesArray();
+ initWorkers();
else if ((q = ws[k = r & m & SQMASK]) != null) {
- if (q.trySharedPush(task))
- return;
- else
- r = 0; // move on contention
+ if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
+ ForkJoinTask>[] a = q.array;
+ int s = q.top;
+ boolean submitted = false;
+ try { // locked version of push
+ if ((a != null && a.length > s + 1 - q.base) ||
+ (a = q.growArray()) != null) { // must presize
+ int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
+ U.putOrderedObject(a, j, task);
+ q.top = s + 1;
+ submitted = true;
+ }
+ } finally {
+ q.qlock = 0; // unlock
+ }
+ if (submitted) {
+ signalWork(q);
+ return;
+ }
+ }
+ r = 0; // move on failure
}
else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
q = new WorkQueue(this, null, SHARED_QUEUE, r);
@@ -1566,17 +1617,13 @@ public class ForkJoinPool extends Abstra
}
/**
- * Tries to create (at most one) or activate (possibly several)
- * workers if too few are active. On contention failure, continues
- * until at least one worker is signalled or the given queue is
- * empty or all workers are active.
- *
- * @param q if non-null, the queue holding tasks to be signalled
- * @param signals the target number of signals (at least one --
- * if argument is zero also sets signallee hint if parked).
+ * Tries to create or activate a worker if too few are active.
+ *
+ * @param q the (non-null) queue holding tasks to be signalled
*/
- final void signalWork(WorkQueue q, int signals) {
- long c; int e, u, i, s; WorkQueue[] ws; WorkQueue w; Thread p;
+ final void signalWork(WorkQueue q) {
+ int hint = q.poolIndex;
+ long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
while ((u = (int)((c = ctl) >>> 32)) < 0) {
if ((e = (int)c) > 0) {
if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
@@ -1584,32 +1631,23 @@ public class ForkJoinPool extends Abstra
long nc = (((long)(w.nextWait & E_MASK)) |
((long)(u + UAC_UNIT) << 32));
if (U.compareAndSwapLong(this, CTL, c, nc)) {
+ w.hint = hint;
w.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = w.parker) != null) {
- if (q != null && signals == 0)
- w.hint = q.poolIndex;
+ if ((p = w.parker) != null)
U.unpark(p);
- }
- if (--signals <= 0)
- break;
+ break;
}
- if (q != null && (s = q.queueSize()) <= signals &&
- (signals = s) <= 0)
+ if (q.top - q.base <= 0)
break;
}
else
break;
}
- else if (e == 0 && (u & SHORT_SIGN) != 0) {
- long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
- ((u + UAC_UNIT) & UAC_MASK)) << 32;
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- addWorker();
- break;
- }
- }
- else
+ else {
+ if ((short)u < 0)
+ tryAddWorker();
break;
+ }
}
}
@@ -1619,8 +1657,8 @@ public class ForkJoinPool extends Abstra
* Top-level runloop for workers, called by ForkJoinWorkerThread.run.
*/
final void runWorker(WorkQueue w) {
- if (w != null) // skip on initialization failure
- do { w.runTask(scan(w)); } while (w.qlock >= 0);
+ w.growArray(); // allocate queue
+ do { w.runTask(scan(w)); } while (w.qlock >= 0);
}
/**
@@ -1659,12 +1697,13 @@ public class ForkJoinPool extends Abstra
* @return a task or null if none found
*/
private final ForkJoinTask> scan(WorkQueue w) {
- WorkQueue[] ws; int m, hint;
+ WorkQueue[] ws; int m;
int ps = plock; // read plock before ws
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;
- for (int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN; ; --j) {
+ int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN;
+ do {
WorkQueue q; ForkJoinTask>[] a; int b;
if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
(a = q.array) != null) { // probably nonempty
@@ -1674,57 +1713,49 @@ public class ForkJoinPool extends Abstra
if (q.base == b && ec >= 0 && t != null &&
U.compareAndSwapObject(a, i, t, null)) {
if ((q.base = b + 1) - q.top < 0)
- signalWork(q, 0);
+ signalWork(q);
return t; // taken
}
- else if (ec < 0 || j < m) { // cannot take or cannot rescan
- w.hint = q.poolIndex; // use hint below
- break; // let caller retry after signal
- }
- }
- else if (j < 0) { // end of scan; in loop to simplify code
- long c, sc; int e, ns;
- if ((ns = w.nsteals) != 0) {
- if (U.compareAndSwapLong(this, STEALCOUNT,
- sc = stealCount, sc + ns))
- w.nsteals = 0; // collect steals
- }
- else if (plock != ps) // ws may have changed
- break;
- 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.hint = -1; // use hint if set while parked
- 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);
- }
- break;
+ else if ((ec < 0 || j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
+ w.hint = (r + j) & m; // help signal below
+ break; // cannot take
+ }
+ }
+ } 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 ((hint = w.hint) >= 0) { // help signal
- WorkQueue[] vs; WorkQueue v; int k;
- w.hint = -1; // suppress resignal
- if ((vs = workQueues) != null && hint < vs.length &&
- (v = vs[hint]) != null && (k = v.base - v.top) < -1)
- signalWork(v, 1 - k);
- }
+ if (h >= 0 || w.hint >= 0) // signal others before retry
+ helpSignalHint(w);
}
return null;
}
@@ -1746,7 +1777,7 @@ public class ForkJoinPool extends Abstra
!tryTerminate(false, false) && (int)prevCtl != 0) {
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()
@@ -1762,7 +1793,6 @@ public class ForkJoinPool extends Abstra
U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
w.qlock = -1; // shrink
- w.hint = -1; // suppress helping
break;
}
}
@@ -1770,28 +1800,77 @@ public class ForkJoinPool extends Abstra
}
/**
- * Scans through queues looking for work (optionally, while
- * joining a task); if any are 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
*/
- final int helpSignal(ForkJoinTask> task, int origin) {
- WorkQueue[] ws; WorkQueue q; int m, n, s, u;
- if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
- for (int i = 0; i <= m; ++i) {
- if (task != null && (s = task.status) < 0)
- return s;
- if ((q = ws[(i + origin) & m]) != null &&
- (n = q.queueSize()) > 0) {
- signalWork(q, n);
- if ((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
+ private void helpSignal(ForkJoinTask> task, int origin) {
+ WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
+ 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 = m; j >= 0; --j) {
+ WorkQueue q = ws[k++ & m];
+ for (int n = m;;) { // limit to at most m signals
+ if (task.status < 0)
+ break outer;
+ if (q == null ||
+ ((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) ||
+ (w = ws[i]) == null)
+ 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)) {
+ w.eventCount = (e + E_SEQ) & E_MASK;
+ if ((p = w.parker) != null)
+ U.unpark(p);
+ if (--n <= 0)
+ break;
+ }
+ }
+ }
+ }
+ }
+
+ /**
+ * Signals other workers if tasks are present in hinted queue.
+ *
+ * @param caller the worker with the hint
+ */
+ private void helpSignalHint(WorkQueue caller) {
+ WorkQueue[] ws; WorkQueue q, w; Thread p; long c; int h, m, u, e, i, s;
+ if (caller != null && (h = caller.hint) >= 0 &&
+ (u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
+ (ws = workQueues) != null && (m = ws.length - 1) >= 0 &&
+ (q = ws[h & m]) != null) {
+ caller.hint = -1;
+ for (int n = 2;;) { // limit to at most 2 signals
+ int idleCount = (caller.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) ||
+ (w = ws[i]) == null)
+ break;
+ long nc = (((long)(w.nextWait & E_MASK)) |
+ ((long)(u + UAC_UNIT) << 32));
+ if (w.eventCount == (e | INT_SIGN) &&
+ U.compareAndSwapLong(this, CTL, c, nc)) {
+ w.hint = h;
+ w.eventCount = (e + E_SEQ) & E_MASK;
+ if ((p = w.parker) != null)
+ U.unpark(p);
+ if (--n <= 0)
break;
}
}
}
- return 0;
}
/**
@@ -1940,8 +2019,19 @@ public class ForkJoinPool extends Abstra
else if (tc + pc < MAX_CAP) {
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
if (U.compareAndSwapLong(this, CTL, c, nc)) {
- addWorker();
- return true;
+ ForkJoinWorkerThreadFactory fac;
+ Throwable ex = null;
+ ForkJoinWorkerThread wt = null;
+ try {
+ if ((fac = factory) != null &&
+ (wt = fac.newThread(this)) != null) {
+ wt.start();
+ return true;
+ }
+ } catch (Throwable rex) {
+ ex = rex;
+ }
+ deregisterWorker(wt, ex); // clean up and return false
}
}
}
@@ -1960,27 +2050,20 @@ public class ForkJoinPool extends Abstra
if (joiner != null && task != null && (s = task.status) >= 0) {
ForkJoinTask> prevJoin = joiner.currentJoin;
joiner.currentJoin = task;
- do {} while ((s = task.status) >= 0 &&
- joiner.queueSize() > 0 &&
+ do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
joiner.tryRemoveAndExec(task)); // process local tasks
- if (s >= 0 && (s = task.status) >= 0 &&
- (s = helpSignal(task, joiner.poolIndex)) >= 0 &&
- (task instanceof CountedCompleter))
- s = helpComplete(task, LIFO_QUEUE);
- int k = 0; // to perform pre-block yield for politeness
+ if (s >= 0 && (s = task.status) >= 0) {
+ helpSignal(task, joiner.poolIndex);
+ if ((s = task.status) >= 0 &&
+ (task instanceof CountedCompleter))
+ s = helpComplete(task, LIFO_QUEUE);
+ }
while (s >= 0 && (s = task.status) >= 0) {
- if ((joiner.queueSize() > 0 || // try helping
+ if ((!joiner.isEmpty() || // try helping
(s = tryHelpStealer(joiner, task)) == 0) &&
(s = task.status) >= 0) {
- if (k < 3) {
- if (++k < 3)
- s = helpSignal(task, joiner.poolIndex);
- else
- Thread.yield();
- }
- else if (!tryCompensate())
- k = 0;
- else {
+ helpSignal(task, joiner.poolIndex);
+ if ((s = task.status) >= 0 && tryCompensate()) {
if (task.trySetSignal() && (s = task.status) >= 0) {
synchronized (task) {
if (task.status >= 0) {
@@ -2017,14 +2100,15 @@ public class ForkJoinPool extends Abstra
if (joiner != null && task != null && (s = task.status) >= 0) {
ForkJoinTask> prevJoin = joiner.currentJoin;
joiner.currentJoin = task;
- do {} while ((s = task.status) >= 0 &&
- joiner.queueSize() > 0 &&
+ do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
joiner.tryRemoveAndExec(task));
- if (s >= 0 && (s = task.status) >= 0 &&
- (s = helpSignal(task, joiner.poolIndex)) >= 0 &&
- (task instanceof CountedCompleter))
- s = helpComplete(task, LIFO_QUEUE);
- if (s >= 0 && joiner.queueSize() == 0) {
+ if (s >= 0 && (s = task.status) >= 0) {
+ helpSignal(task, joiner.poolIndex);
+ if ((s = task.status) >= 0 &&
+ (task instanceof CountedCompleter))
+ s = helpComplete(task, LIFO_QUEUE);
+ }
+ if (s >= 0 && joiner.isEmpty()) {
do {} while (task.status >= 0 &&
tryHelpStealer(joiner, task) > 0);
}
@@ -2046,9 +2130,9 @@ public class ForkJoinPool extends Abstra
return null;
for (int j = (m + 1) << 2; ;) {
WorkQueue q = ws[(((r + j) << 1) | 1) & m];
- if (q != null && (n = q.queueSize()) > 0) {
- if (n > 1)
- signalWork(q, 0);
+ if (q != null && (n = q.base - q.top) < 0) {
+ if (n < -1)
+ signalWork(q);
return q;
}
else if (--j < 0) {
@@ -2290,24 +2374,26 @@ public class ForkJoinPool extends Abstra
*/
static boolean tryExternalUnpush(ForkJoinTask> t) {
ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
- ForkJoinTask>[] a; int m, s; long j;
- if ((z = submitters.get()) != null &&
+ ForkJoinTask>[] a; int m, s;
+ if (t != null &&
+ (z = submitters.get()) != null &&
(p = commonPool) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0 &&
(q = ws[m & z.seed & SQMASK]) != null &&
(s = q.top) != q.base &&
- (a = q.array) != null &&
- U.getObjectVolatile
- (a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
- U.compareAndSwapInt(q, QLOCK, 0, 1)) {
- if (q.array == a && q.top == s && // recheck
- U.compareAndSwapObject(a, j, t, null)) {
- q.top = s - 1;
+ (a = q.array) != null) {
+ long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
+ if (U.getObject(a, j) == t &&
+ U.compareAndSwapInt(q, QLOCK, 0, 1)) {
+ if (q.array == a && q.top == s && // recheck
+ U.compareAndSwapObject(a, j, t, null)) {
+ q.top = s - 1;
+ q.qlock = 0;
+ return true;
+ }
q.qlock = 0;
- return true;
}
- q.qlock = 0;
}
return false;
}
@@ -2349,7 +2435,8 @@ public class ForkJoinPool extends Abstra
(u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
break;
if (task == null) {
- if (helpSignal(root, q.poolIndex) >= 0)
+ helpSignal(root, q.poolIndex);
+ if (root.status >= 0)
helpComplete(root, SHARED_QUEUE);
break;
}
@@ -2364,27 +2451,28 @@ public class ForkJoinPool extends Abstra
static void externalHelpJoin(ForkJoinTask> t) {
// Some hard-to-avoid overlap with tryExternalUnpush
ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
- ForkJoinTask>[] a; int m, s, n; long j;
+ ForkJoinTask>[] a; int m, s, n;
if (t != null &&
(z = submitters.get()) != null &&
(p = commonPool) != null &&
(ws = p.workQueues) != null &&
(m = ws.length - 1) >= 0 &&
(q = ws[m & z.seed & SQMASK]) != null &&
- (a = q.array) != null &&
- t.status >= 0) {
- if ((s = q.top) != q.base &&
- U.getObjectVolatile
- (a, j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE) == t &&
- U.compareAndSwapInt(q, QLOCK, 0, 1)) {
- if (q.array == a && q.top == s &&
- U.compareAndSwapObject(a, j, t, null)) {
- q.top = s - 1;
- q.qlock = 0;
- t.doExec();
+ (a = q.array) != null) {
+ int am = a.length - 1;
+ if ((s = q.top) != q.base) {
+ long j = ((am & (s - 1)) << ASHIFT) + ABASE;
+ if (U.getObject(a, j) == t &&
+ U.compareAndSwapInt(q, QLOCK, 0, 1)) {
+ if (q.array == a && q.top == s &&
+ U.compareAndSwapObject(a, j, t, null)) {
+ q.top = s - 1;
+ q.qlock = 0;
+ t.doExec();
+ }
+ else
+ q.qlock = 0;
}
- else
- q.qlock = 0;
}
if (t.status >= 0) {
if (t instanceof CountedCompleter)
@@ -2480,7 +2568,7 @@ public class ForkJoinPool extends Abstra
throw new IllegalArgumentException();
this.factory = factory;
this.ueh = handler;
- this.config = parallelism | (asyncMode? (FIFO_QUEUE << 16) : 0);
+ this.config = parallelism | (asyncMode ? (FIFO_QUEUE << 16) : 0);
long np = (long)(-parallelism); // offset ctl counts
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
int pn = nextPoolId();
@@ -2838,7 +2926,7 @@ public class ForkJoinPool extends Abstra
WorkQueue[] ws; WorkQueue w;
if ((ws = workQueues) != null) {
for (int i = 0; i < ws.length; i += 2) {
- if ((w = ws[i]) != null && w.queueSize() != 0)
+ if ((w = ws[i]) != null && !w.isEmpty())
return true;
}
}
@@ -3005,7 +3093,7 @@ public class ForkJoinPool extends Abstra
* commenced but not yet completed. This method may be useful for
* debugging. A return of {@code true} reported a sufficient
* period after shutdown may indicate that submitted tasks have
- * ignored or suppressed interruption, or are waiting for IO,
+ * ignored or suppressed interruption, or are waiting for I/O,
* causing this executor not to properly terminate. (See the
* advisory notes for class {@link ForkJoinTask} stating that
* tasks should not normally entail blocking operations. But if
@@ -3160,13 +3248,13 @@ public class ForkJoinPool extends Abstra
if (t instanceof ForkJoinWorkerThread) {
ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
while (!blocker.isReleasable()) { // variant of helpSignal
- WorkQueue[] ws; WorkQueue q; int m, n, u;
+ WorkQueue[] ws; WorkQueue q; int m, u;
if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
for (int i = 0; i <= m; ++i) {
if (blocker.isReleasable())
return;
- if ((q = ws[i]) != null && (n = q.queueSize()) > 0) {
- p.signalWork(q, n);
+ if ((q = ws[i]) != null && q.base - q.top < 0) {
+ p.signalWork(q);
if ((u = (int)(p.ctl >>> 32)) >= 0 ||
(u >> UAC_SHIFT) >= 0)
break;
@@ -3245,6 +3333,8 @@ public class ForkJoinPool extends Abstra
submitters = new ThreadLocal();
ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
new DefaultForkJoinWorkerThreadFactory();
+ modifyThreadPermission = new RuntimePermission("modifyThread");
+
/*
* Establish common pool parameters. For extra caution,
* computations to set up common pool state are here; the
@@ -3280,7 +3370,6 @@ public class ForkJoinPool extends Abstra
long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
commonPool = new ForkJoinPool(par, ct, fac, handler);
- modifyThreadPermission = new RuntimePermission("modifyThread");
}
/**