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More policy exploration
This commit is contained in:
Doug Lea
parent
50b81c4549
commit
5f84c2a980
@ -1933,66 +1933,62 @@ public class ForkJoinPool extends AbstractExecutorService
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if (w != null) {
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int r = w.stackPred; // seed from registerWorker
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int fifo = (int)config & FIFO;
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for (int idle = 0, taken = 0, src = -1;;) {
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for (int nsteals = 0, idle = 0, src = -1;;) {
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WorkQueue[] qs; int n, j;
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r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // xorshift
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long e = runState;
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if ((qs = queues) == null ||
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(j = ((n = qs.length) << 1)) <= 0 || // 2 sweeps per scan
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(e & STOP) != 0L) {
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w.nsteals += taken;
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(e & STOP) != 0L)
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return;
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}
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scan: for (int i = r, step = (r >>> 16) | 1; ; i += step) {
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WorkQueue q; int qid;
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if ((q = qs[qid = i & (n - 1)]) != null) {
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for (int pb = -1, found = 0;;) {
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ForkJoinTask<?> t;
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ForkJoinTask<?>[] a = q.array;
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int b = q.base, cap, nb;
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if (a == null || (cap = a.length) <= 0)
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break;
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long np = slotOffset((cap - 1) & (nb = b + 1)), bp;
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ForkJoinTask<?>[] a; int pb = -1, taken = 0, cap;
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while ((a = q.array) != null && (cap = a.length) > 0) {
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ForkJoinTask<?> t; int b, nb, prevSrc; long bp;
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t = (ForkJoinTask<?>)U.getReferenceAcquire(
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a, bp = slotOffset((cap - 1) & b));
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if (q.array != a || q.base != b ||
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U.getReference(a, bp) != t)
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; // inconsistent
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else if (t == null ||
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(idle == 0 &&
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!U.compareAndSetReference(a, bp, t, null))) {
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if (U.getReference(a, np) == null) {
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if (found != 0) // end of run
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a, bp = slotOffset((cap - 1) & (b = q.base)));
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if (q.array == a && q.base == b) { // else inconsistent
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long np = slotOffset((cap - 1) & (nb = b + 1));
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if (t == null ||
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(idle == 0 &&
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!U.compareAndSetReference(a, bp, t, null))) {
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if (taken != 0) { // end of run
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w.nsteals = nsteals += taken;
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break scan;
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break; // probably empty
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}
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if (U.getReference(a, bp) == null) {
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if (U.getReference(a, np) == null)
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break; // probably empty
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if (pb == (pb = b))
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break scan; // stalled; reorder scan
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}
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}
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else if (idle != 0) {
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if ((idle = tryReactivate(w)) != 0)
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break scan; // can't take yet
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}
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else {
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q.base = nb;
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Object nt = U.getReferenceVolatile(a, np);
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if (qid != (prevSrc = src))
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w.source = src = qid;
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++taken;
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if (nt != null && (prevSrc < 0 || fifo != 0) &&
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U.getReference(a, np) != null)
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signalWork(q, nb);
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w.topLevelExec(t, fifo);
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}
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if (pb == (pb = b)) // track progress
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break scan; // stalled; reorder scan
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}
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else if (idle != 0) {
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found = 1;
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if ((idle = tryReactivate(w)) != 0)
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break scan; // can't take yet
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}
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else {
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boolean propagate;
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q.base = nb;
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Object nt = U.getReferenceVolatile(a, np);
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if (qid != src)
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w.source = src = qid;
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found = 1;
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if (propagate =
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((++taken == 1 || fifo != 0) &&
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nt != null && U.getReference(a, np) != null))
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signalWork(q, nb);
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w.topLevelExec(t, fifo);
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}
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}
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}
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if (--j == 0) { // empty scan
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if ((idle = deactivate(w, idle, taken)) == -1)
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if (idle == 0)
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idle = tryDeactivate(w, src);
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else if ((idle = awaitWork(w)) != 0)
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return; // trimmed or terminated
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taken = 0;
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src = -1;
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break;
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}
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}
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@ -2004,50 +2000,51 @@ public class ForkJoinPool extends AbstractExecutorService
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* Possibly deactivates worker.
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*
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* @param w the work queue
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* @param idle current idle status
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* @param taken number of tasks stolen since last call
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* @return idle status or -1 for exit
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* @return idle status
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*/
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private int deactivate(WorkQueue w, int idle, int taken) {
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private int tryDeactivate(WorkQueue w, int src) {
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int idle = 0;
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if (w != null) { // always true; hoist checks
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int phase = w.phase;
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if (taken != 0) { // postpone
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w.nsteals += taken;
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if ((w.config & CLEAR_TLS) != 0 &&
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(Thread.currentThread() instanceof ForkJoinWorkerThread f))
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f.resetThreadLocals(); // (instanceof check always true)
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Thread.interrupted(); // clear status
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}
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else if (idle == 0) {
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long sp = (phase + NEXTIDLE) & LMASK, pc = ctl;
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U.putInt(w, WorkQueue.PHASE, phase | IDLE);
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for (;;) { // enqueue
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w.stackPred = (int)pc;
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long c = (pc - RC_UNIT) & UMASK | sp, ac = c & RC_MASK;
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if (pc == (pc = U.compareAndExchangeLong(this, CTL, pc, c))) {
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if (ac <= 0L && (runState & (SHUTDOWN|STOP)) == SHUTDOWN)
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if (src >= 0 && (w.config & CLEAR_TLS) != 0 &&
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(Thread.currentThread() instanceof ForkJoinWorkerThread f))
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f.resetThreadLocals(); // (instanceof check always true)
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int phase = U.getInt(w, WorkQueue.PHASE);
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long sp = (phase + NEXTIDLE) & LMASK, pc = ctl;
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U.putInt(w, WorkQueue.PHASE, phase | IDLE);
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for (;;) { // enqueue
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w.stackPred = (int)pc;
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long c = (pc - RC_UNIT) & UMASK | sp, ac = c & RC_MASK;
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if (pc == (pc = U.compareAndExchangeLong(this, CTL, pc, c))) {
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if (ac == 0L) {
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if ((runState & (SHUTDOWN|STOP)) == SHUTDOWN)
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quiescent(); // check quiescent termination
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idle = w.phase & IDLE;
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break;
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}
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else if (ac < (pc & RC_MASK)) {
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w.phase = phase; // back out if lost to signal
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break;
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else {
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int tc = ((short)(c >>> TC_SHIFT) | 1) & SMASK;
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int spins = tc + Math.max(tc << 1, SPIN_WAITS);
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while ((idle = w.phase & IDLE) != 0 && --spins != 0)
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Thread.onSpinWait(); // spin for approx 1 scan cost
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}
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break;
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}
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else if (ac < (pc & RC_MASK)) {
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w.phase = phase; // back out if lost to signal
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break;
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}
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}
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else if ((idle = phase & IDLE) != 0)
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idle = awaitWork(w, phase);
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}
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return idle;
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}
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/**
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* Reactivates worker w if it is currently top of ctl stack
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*
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* @param w the work queue
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* @return 0 if now active
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*/
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@jdk.internal.vm.annotation.DontInline // avoid prefetch of contending memory
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private int tryReactivate(WorkQueue w) {
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int idle = 0;
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if (w != null) { // always true; hoist checks
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@ -2070,12 +2067,11 @@ public class ForkJoinPool extends AbstractExecutorService
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* Awaits signal or termination.
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*
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* @param w the work queue
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* @param phase current (inactive) phase
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* @return 0 if now active else -1
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*/
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private int awaitWork(WorkQueue w, int phase) {
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int idle = IDLE;
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if (w != null) { // always true; hoist checks
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private int awaitWork(WorkQueue w) {
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int idle = IDLE, phase;
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if (w != null && (idle = (phase = w.phase) & IDLE) != 0) {
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int activePhase = phase + IDLE, trim;
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if ((trim = w.trimStatus) != 0)
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w.trimStatus = 0;
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@ -2107,7 +2103,7 @@ public class ForkJoinPool extends AbstractExecutorService
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Thread.interrupted(); // clear status for next park
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}
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}
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return (idle != 0) ? -1 : 0;
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return idle;
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}
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/**
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