JDK-8230459: Test failed to resume JVMCI CompilerThread

[Doerr, Martin]

Hi David,

>> As C1 and C2 compiler threads are hidden, I still don't see any problems reusing the Thread objects.
> They are not completely hidden. Those j.l.Thread objects are still part of the system thread group and can be found by other code.

I know that they are part of the system thread group, but I thought they should not be visible to Java.

E.g.
        ThreadGroup tg = new ThreadGroup("A");
        ThreadGroup stg = tg.getParent().getParent();
        Thread[] list = new Thread[100];
        stg.enumerate(list);
        System.out.println("Listing elements of " + stg);
        for (int i = 0; i < list.length; ++i) {
            if (list[i] != null) {
                System.out.println(i + ": " + list[i]);
            }
        }

Finds:
Listing elements of java.lang.ThreadGroup[name=system,maxpri=10]
0: Thread[Reference Handler,10,system]
1: Thread[Finalizer,8,system]
2: Thread[Signal Dispatcher,9,system]
3: Thread[main,5,main]

I can't see any compiler threads.

Do you mean finding them by JVMTI agent?
As I understand the Spec, compiler threads should be excluded for GetAllThreads: "The threads are Java programming language threads"

Or what did you mean by "other code" which can see C1 and C2 threads?

Best regards,
Martin