RFR: 8234010: ZGC: Change ZResurrection to use Atomic::load/store

[Stefan Karlsson]

Hi all,

Please review this patch to change ZResurrection to use Atomic::load and 
Atomic::store.

https://cr.openjdk.java.net/~stefank/8234010/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8234010

Previously, ZResurrection::is_blocked() and ZResurrection::unblock() 
used loadload and storestore barriers to synchronize between the GC and 
mutator load barriers.

JDK-8230661 changed so that we always perform a handshake before the 
ZResurrection::unblock() call.

After that change we can rely on the handshake to perform the necessary 
synchronization, and we can change the implementation to use 
Atomic::load and Atomic::store.

Tested with tier1-7

Thanks,
StefanK