RFR: 8253180: ZGC: Implementation of JEP 376: ZGC: Concurrent Thread-Stack Processing [v7]

[Roman Kennke]

On Tue, 29 Sep 2020 07:28:20 GMT, Per Liden <pliden at openjdk.org> wrote:

>> FTR, this is the RFE to remove the oop verification from the oop_iterate framework:
>> https://bugs.openjdk.java.net/browse/JDK-8237363
>> 
>> I really would like to get rid of it, but got push back because it made GCs have to duplicate the effort to provide
>> verification.
>
> I've also has problems with this assert in the past, and I think that the underlying assumption of the assert is wrong.
> I would not miss it.

IMO it's ok to remove it.
However, it can be argued that is_in() should not check for 'in committed memory' but 'in reserved space for heap', IOW
'is this a pointer into our heap memory region?'.  Or maybe this would be CH::is_in_reserved() and we should change the
assert to that? Also, IMO we should not do anything that may trip barriers on oop-iterators or similar GC-only paths.

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PR: https://git.openjdk.java.net/jdk/pull/296