[foreign-memaccess+abi] RFR: 8263018: Improve API for lifecycle of native resources [v10]

[Maurizio Cimadamore]

On Fri, 12 Mar 2021 10:33:07 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/ArenaAllocator.java line 9:
>> 
>>> 7: import java.util.OptionalLong;
>>> 8: 
>>> 9: public class ArenaAllocator implements SegmentAllocator {
>> 
>> The implementations are not thread safe. Do we need to adjust the specification on SegmentAllocator accordingly?
>
> I believe here there is some effort towards making everything thread-safe - in the sense that, based on the scope provided by the client (confined or shared) a different kind of allocator impl will be returned to the user. A shared bounded arena has a synchronized allocation method - while a shared unbound segment uses multiple underlying thread-local allocators.
> 
> Perhaps you refer to the fact that we don't check (in confined cases) that we are in the same thread as the scope's thread _before_ responding to an allocation request?

I've added confinement check in latest iteration

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PR: https://git.openjdk.java.net/panama-foreign/pull/466