RFR: 8373118: Test java/lang/Thread/virtual/Starvation.java timed out [v26]

[Viktor Klang]

On Wed, 14 Jan 2026 12:41:50 GMT, Doug Lea <dl at openjdk.org> wrote:

>> Changes signal filtering to avoid possible starvation
>
> Doug Lea has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Another set of contend vs deactivate vs park tradeoffs

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 1861:

> 1859:                 break;
> 1860:         }
> 1861:     }

The following might be a potential alternative encoding of signalWork—it would be interesting to hear if it makes any difference on your testing array, Doug:


    final void signalWork(WorkQueue src, int base) {
        int pc = parallelism, i, sp; // rely on caller sync for initial reads
        long c = U.getLong(this, CTL);
        WorkQueue[] qs;
        while ((short)(c >>> RC_SHIFT) < pc && (qs = queues) != null &&
               qs.length > (i = (sp = (int)c) & SMASK) && (src == null || src.base - base < 1)) {
            if (i == 0) {
                if ((short)(c >>> TC_SHIFT) >= pc)
                    break;
                if (c == (c = U.compareAndExchangeLong(this, CTL, c, ((c + TC_UNIT) & TC_MASK) | ((c + RC_UNIT) & RC_MASK)))) {
                    createWorker();
                    break;
                }
            }
            else {
                WorkQueue v;
                if ((v = qs[i]) == null)
                    break;
                if (c == (c = U.compareAndExchangeLong(this, CTL, c, (v.stackPred & LMASK) | ((c + RC_UNIT) & UMASK)))) {
                    v.phase = sp;
                    if (v.parking != 0)
                        U.unpark(v.owner);
                    break;
                }
            }
        }
    }

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/28797#discussion_r2694226850