RFR: 8219613: Use NonJavaThread PtrQueues

[Kim Barrett]

> On Feb 26, 2019, at 5:53 PM, zgu at redhat.com wrote:
> Yes, we current use other mechanism to initialize worker's gclab, so it
> works correctly right now. I were hoping I could use on_thread_xxx
> mechanism to replace our mechanism, so we can simplify a few things.
> 
> I still have a couple of concerns regarding current on_thread_xxx
> implementation.
> 
> 1) on_thread_create() callback, actually sees partially constructed
> thread if the thread is a subclass of Thread.

(Since Thread is (at least conceptually) abstract, the object is
necessarily an instance of a derived class.)

on_thread_create is intended to be called as part of construction.
Similarly on_thread_destroy and destruction.


> 2) For JavaThread, on_thread_attach() is called from creator's thread,
> but non-Java thread is from the thread itself.

If this is a problem, you could add a handshake between the creator
and the new thread's run function, so the creator knows the new thread
has been added to the thread list before proceeding to use it.