a-foundation-benchmark/src/main/java/com/ajjpj/afoundation/concurrent/jdk/j9new/ForkJoinPool.java
private ForkJoinTask<?> scan(WorkQueue w, int r) {
        WorkQueue[] ws; int m;
        if ((ws = workQueues) != null && (m = ws.length - 1) > 0 && w != null) {
            int ss = w.scanState;                     // initially non-negative
            for (int origin = r & m, k = origin, oldSum = 0, checkSum = 0;;) {
                WorkQueue q; ForkJoinTask<?>[] a; ForkJoinTask<?> t;
                int b, n; long c;
                if ((q = ws[k]) != null) {
                    if ((n = (b = q.base) - q.top) < 0 &&
                        (a = q.array) != null) {      // non-empty
                        long i = (((a.length - 1) & b) << ASHIFT) + ABASE;
                        if ((t = ((ForkJoinTask<?>)
                                  U.getObjectVolatile(a, i))) != null &&
                            q.base == b) {
                            if (ss >= 0) {
                                if (U.compareAndSwapObject(a, i, t, null)) {
                                    q.base = b + 1;
                                    if (n < -1)       // signal others
                                        signalWork(ws, q);
                                    return t;
                                }
                            }
                            else if (oldSum == 0 &&   // try to activate
                                     w.scanState < 0)
                                tryRelease(c = ctl, ws[m & (int)c], AC_UNIT);
                        }
                        if (ss < 0)                   // refresh
                            ss = w.scanState;
                        r ^= r << 1; r ^= r >>> 3; r ^= r << 10;
                        origin = k = r & m;           // move and rescan
                        oldSum = checkSum = 0;
                        continue;
                    }
                    checkSum += b;
                }
                if ((k = (k + 1) & m) == origin) {    // continue until stable
                    if ((ss >= 0 || (ss == (ss = w.scanState))) &&
                        oldSum == (oldSum = checkSum)) {
                        if (ss < 0 || w.qlock < 0)    // already inactive
                            break;
                        int ns = ss | INACTIVE;       // try to inactivate
                        long nc = ((SP_MASK & ns) |
                                   (UC_MASK & ((c = ctl) - AC_UNIT)));
                        w.stackPred = (int)c;         // hold prev stack top
                        U.putInt(w, QSCANSTATE, ns);
                        if (U.compareAndSwapLong(this, CTL, c, nc))
                            ss = ns;
                        else
                            w.scanState = ss;         // back out
                    }
                    checkSum = 0;
                }
            }
        }
        return null;
    }
private ForkJoinTask<?> scan(WorkQueue w, int r) {
        WorkQueue[] ws; int m;
        if ((ws = workQueues) != null && (m = ws.length - 1) > 0 && w != null) {
            int ss = w.scanState;                     // initially non-negative
            for (int origin = r & m, k = origin, oldSum = 0, checkSum = 0;;) {
                WorkQueue q; ForkJoinTask<?>[] a; ForkJoinTask<?> t;
                int b, n; long c;
                if ((q = ws[k]) != null) {
                    if ((n = (b = q.base) - q.top) < 0 &&
                        (a = q.array) != null) {      // non-empty
                        long i = (((a.length - 1) & b) << ASHIFT) + ABASE;
                        if ((t = ((ForkJoinTask<?>)
                                  U.getObjectVolatile(a, i))) != null &&
                            q.base == b) {
                            if (ss >= 0) {
                                if (U.compareAndSwapObject(a, i, t, null)) {
                                    q.base = b + 1;
                                    if (n < -1)       // signal others
                                        signalWork(ws, q);
                                    return t;
                                }
                            }
                            else if (oldSum == 0 &&   // try to activate
                                     w.scanState < 0)
                                tryRelease(c = ctl, ws[m & (int)c], AC_UNIT);
                        }
                        if (ss < 0)                   // refresh
                            ss = w.scanState;
                        r ^= r << 1; r ^= r >>> 3; r ^= r << 10;
                        origin = k = r & m;           // move and rescan
                        oldSum = checkSum = 0;
                        continue;
                    }
                    checkSum += b;
                }
                if ((k = (k + 1) & m) == origin) {    // continue until stable
                    if ((ss >= 0 || (ss == (ss = w.scanState))) &&
                        oldSum == (oldSum = checkSum)) {
                        if (ss < 0 || w.qlock < 0)    // already inactive
                            break;
                        int ns = ss | INACTIVE;       // try to inactivate
                        long nc = ((SP_MASK & ns) |
                                   (UC_MASK & ((c = ctl) - AC_UNIT)));
                        w.stackPred = (int)c;         // hold prev stack top
                        U.putInt(w, QSCANSTATE, ns);
                        if (U.compareAndSwapLong(this, CTL, c, nc))
                            ss = ns;
                        else
                            w.scanState = ss;         // back out
                    }
                    checkSum = 0;
                }
            }
        }
        return null;
    }
private ForkJoinTask < ? > scan ( WorkQueue w , int r ) { WorkQueue [ ] ws ; int m ; if ( ( ws = workQueues ) != null && ( m = ws . length - 1 ) > 0 && w != null ) { int ss = w . scanState ; // initially non-negative for ( int origin = r & m , k = origin , oldSum = 0 , checkSum = 0 ; ; ) { WorkQueue q ; ForkJoinTask < ? > [ ] a ; ForkJoinTask < ? > t ; int b , n ; long c ; if ( ( q = ws [ k ] ) != null ) { if ( ( n = ( b = q . base ) - q . top ) < 0 && ( a = q . array ) != null ) { // non-empty long i = ( ( ( a . length - 1 ) & b ) << ASHIFT ) + ABASE ; if ( ( t = ( ( ForkJoinTask < ? > ) U . getObjectVolatile ( a , i ) ) ) != null && q . base == b ) { if ( ss >= 0 ) { if ( U . compareAndSwapObject ( a , i , t , null ) ) { q . base = b + 1 ; if ( n < - 1 ) // signal others signalWork ( ws , q ) ; return t ; } } else if ( oldSum == 0 && // try to activate w . scanState < 0 ) tryRelease ( c = ctl , ws [ m & ( int ) c ] , AC_UNIT ) ; } if ( ss < 0 ) // refresh ss = w . scanState ; r ^= r << 1 ; r ^= r >>> 3 ; r ^= r << 10 ; origin = k = r & m ; // move and rescan oldSum = checkSum = 0 ; continue ; } checkSum += b ; } if ( ( k = ( k + 1 ) & m ) == origin ) { // continue until stable if ( ( ss >= 0 || ( ss == ( ss = w . scanState ) ) ) && oldSum == ( oldSum = checkSum ) ) { if ( ss < 0 || w . qlock < 0 ) // already inactive break ; int ns = ss | INACTIVE ; // try to inactivate long nc = ( ( SP_MASK & ns ) | ( UC_MASK & ( ( c = ctl ) - AC_UNIT ) ) ) ; w . stackPred = ( int ) c ; // hold prev stack top U . putInt ( w , QSCANSTATE , ns ) ; if ( U . compareAndSwapLong ( this , CTL , c , nc ) ) ss = ns ; else w . scanState = ss ; // back out } checkSum = 0 ; } } } return null ; }
Scans for and tries to steal a top-level task. Scans start at a
random location, randomly moving on apparent contention,
otherwise continuing linearly until reaching two consecutive
empty passes over all queues with the same checksum (summing
each base index of each queue, that moves on each steal), at
which point the worker tries to inactivate and then re-scans,
attempting to re-activate (itself or some other worker) if
finding a task; otherwise returning null to await work.  Scans
otherwise touch as little memory as possible, to reduce
disruption on other scanning threads.

@param w the worker (via its WorkQueue)
@param r a random seed
@return a task, or null if none found
Scans for and tries to steal a top - level task . Scans start at a random location randomly moving on apparent contention otherwise continuing linearly until reaching two consecutive empty passes over all queues with the same checksum ( summing each base index of each queue that moves on each steal ) at which point the worker tries to inactivate and then re - scans attempting to re - activate ( itself or some other worker ) if finding a task ; otherwise returning null to await work . Scans otherwise touch as little memory as possible to reduce disruption on other scanning threads .