RFR: 8308745: ObjArrayKlass::allocate_objArray_klass may call into java while holding a lock [v2]

[Coleen Phillimore]

On Thu, 7 Mar 2024 00:18:53 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Dean's comments.
>
> src/hotspot/share/oops/arrayKlass.cpp line 135:
> 
>> 133:     ResourceMark rm(THREAD);
>> 134:     {
>> 135:       // Ensure atomic creation of higher dimensions
> 
> Isn't this comment still useful?

Yes, it's a useful comment, readded.

> src/hotspot/share/oops/arrayKlass.cpp line 144:
> 
>> 142:         ObjArrayKlass* ak =
>> 143:           ObjArrayKlass::allocate_objArray_klass(class_loader_data(), dim + 1, this, CHECK_NULL);
>> 144:         ak->set_lower_dimension(this);
> 
> Would it be useful to assert that the lower dimension has been set?

Yes, added.

> src/hotspot/share/oops/instanceKlass.cpp line 2765:
> 
>> 2763:     // To get a consistent list of classes we need MultiArray_lock to ensure
>> 2764:     // array classes aren't observed while they are being restored.
>> 2765:     MutexLocker ml(MultiArray_lock);
> 
> Doesn't this revert JDK-8274338?

You're right. I didn't believe my own comment when I removed this.  Thank you for pointing out the bug.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17739#discussion_r1515346198
PR Review Comment: https://git.openjdk.org/jdk/pull/17739#discussion_r1515346716
PR Review Comment: https://git.openjdk.org/jdk/pull/17739#discussion_r1515349878