RFR: 8277216: Examine InstanceKlass::_misc_flags for concurrency issues [v3]

[David Holmes]

On Wed, 15 Dec 2021 20:06:41 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Recent bug in misc_flags showed that they are not set concurrently and could cause bugs.  Most of the misc_flags are set at classfile parsing time or at a safepoint and never reset.  This change adds an assert that the flag is set once.  See CR for more details.
>> Tested with tier1-3.
>
> Coleen Phillimore has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'master' into misc
>  - Fix typo.
>  - Move has_resolved_methods to access flags so can be set and tested concurretly.
>  - Move has_resolved_methods to access flags so can be set and tested concurretly.
>  - 8277216: Examine InstanceKlass::_misc_flags for concurrency issues

Hi Coleen,

I like the intent here but the assertions only partially work. Given something like:

void set_has_nonstatic_fields(bool b)    {
assert(!has_nonstatic_fields(), "set once");

then you can still call the set function multiple times if passing false as the argument.

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PR: https://git.openjdk.java.net/jdk/pull/6851