RFR: 8223056: Remove Type-Stable-Memory support for Parkers [v2]

[Coleen Phillimore]

On Wed, 20 Jan 2021 06:18:02 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> As per the bug report, once we ensure the calls to unpark() are guaranteed to only occur on a live thread (protected by a ThreadsListHandle) Parkers (the synchronization object underlying java.util.concurrent.LockSupport) no longer need to use type-stable-memory (TSM).
>> 
>> As a Parker is inherently associated with a single JavaThread, the Parker is now embedded directly in JavaThread, avoiding the need to use new/delete.
>> 
>> The Parker and PlatformParker classes are now simplified from a memory management perspective. I also made them NONCOPYABLE for good measure. Possibly other constraints could be applied to them such as disallowing new/delete? (Though if we go that far maybe we need a new allocation base type?).
>> 
>> Testing: tiers 1-3 plus additional test builds
>> 
>> Thanks,
>> David
>
> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address Coleen's nit.
>   Move _counter field to Posix PlatformParker class.
>   Rename _ParkEvent to _ParkerEvent on Windows

Nice cleanup! Thanks!

src/hotspot/os/windows/os_windows.hpp line 195:

> 193: 
> 194:  protected:
> 195:   HANDLE _ParkerEvent;

How about calling it _ParkHandle like PlatformEvent above it?  Two letters for me is not quickly distinguishable.  If you make this change I don't need to see another version.

-------------

Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2089