RFR: 8291555: Implement alternative fast-locking scheme [v29]

[Erik Österlund]

On Mon, 27 Mar 2023 15:53:47 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> > @rkennke Question about ZGC and LockStack::contains(): how does this work with colored pointers? Don't we have to mask the color bits out somehow when comparing? E.g. using `ZAddress::offset()` ?
> 
> 
> 
> That would be a question for @fisk and/or @stefank. AFAIK, the color bits should be masked by ZGC barriers *before* the oops enter the synchronization subsystem. But I kinda suspect that we are somehow triggering a ZGC bug here. Maybe we require barriers when reading oops from the lock-stack too?

Oops that are processed in Thread::oops_do should not have load barriers. Other oops should have load barriers.

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PR Comment: https://git.openjdk.org/jdk/pull/10907#issuecomment-1485426029