RFR (S) 8178336: Unnecessary SystemDictionary walk for Protection domain liveness

[Jiangli Zhou]

Hi Coleen,

I noticed there are two comments in Dictionary::do_unloading() refer to always_strong_oops_do. They should be updated as well.

150   // The placeholder array has been handled in always_strong_oops_do.
160       // Non-unloadable classes were handled in always_strong_oops_do
Thanks,
Jiangli

> On Apr 10, 2017, at 1:18 PM, coleen.phillimore at oracle.com wrote:
> 
> Summary: remove system dictionary walk and pass strong closure for !ClassUnloading
> 
> See bug for more details:
> 
> open webrev at http://cr.openjdk.java.net/~coleenp/8178336.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8178336
> 
> Tested with nightly tier2-5 tests and jprt (runs all GCs) and runThese with -XX:-ClassUnloading.
> 
> Thanks,
> Coleen