RFR: 8247281: migrate ObjectMonitor::_object to OopStorage [v2]

[Erik Österlund]

On Mon, 14 Sep 2020 14:24:02 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> > @rkennke - Thanks for the review. I believe @fisk is going to address
> > your comments.
> 
> Actually, if I understand it correctly, OopStorage already gives us full barriers, so we should be covered, and we can
> simply revert JDK-8251451: http://cr.openjdk.java.net/~rkennke/8247281-shenandoah.patch
> (Is there a better way to propose amendments to a PR?!)
> 
> I believe this probably also means that we don't need to scan object monitor lists during thread-scans, and let SATB
> (or whatever concurrent marking) take care of it. @fisk WDYT?

Absolutely. GC should no longer have to know anything about ObjectMonitors, only the automatically plugged in
OopStorage that it processes. GC should not walk any monitor lists at all.

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PR: https://git.openjdk.java.net/jdk/pull/135