Work-in-progress: 8236485: Epoch synchronization protocol for G1 concurrent refinement

[Florian Weimer]

* Man Cao:

> We had an offline discussion on this. To keep the community in the loop,
> here is what we discussed.
>
> a. Using Linux membarrier syscall or equivalent on other OSes seems a
> cleaner solution than thread-local handshake (TLH). But we need to have a
> backup mechanism for OSes and older Linuxes that do not have such a
> syscall.

Can you do with a membarrier call that doesn't require registration?

The usual fallback for membarrier is sending a special signal to all
threads, and make sure that they have run code in a signal handler
(possibly using a CPU barrier there).  But of course this is rather
slow.

membarrier has seen some backporting activity, but as far as I can see,
that hasn't been consistent across architectures.

Thanks,
Florian