RFR: JDK-8212186: JVMTI lacks a few GC barriers/hooks

[David Holmes]

Hi Roman, Erik,

On 17/10/2018 7:48 PM, Roman Kennke wrote:
> Erik recently pointed out that  JvmtiTagHashmapEntry::equals() is
> lacking on obj-equals-barrier, and that JvmtiTagHashmap::hash() better
> does ::resolve() the object to a stable value before casting it to a raw
> address.

Can the resolve be incorporated into the cast_from_oop? It's just not 
obvious to me how one realizes when the resolve is necessary. ??

> This lead us to do some more JVMTI testing and we found that we have a
> little inconsistency with reporting object size too: the VMObjectAlloc
> callback now reports a different size that GetObjectSize(). This is also
> fixed by this proposed change:

So when is it valid to use obj->size() and when not?

Thanks,
David
-----

> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8212186
> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8212186/webrev.00/
> 
> Testing: hotspot/tier1, nsk/jvmti with Shenandoah
> 
> Ok?
> 
> Roman
>