RFR: 8264644: Add PrintClassLoaderDataGraphAtExit to print the detailed CLD graph [v3]

[Yi Yang]

On Fri, 2 Apr 2021 12:47:04 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Yi Yang has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - add CLDG_lock
>>  - use PTR_FORMAT
>
> This looks nice. If you use -XX:+PrintSystemDictionaryAtExit with this change, is it pages and pages long?  Or does it look ok?  Thank you for doing this!

Thanks @coleenp @dholmes-ora for your reviews.

For @coleenp : It looks Universe::verify is already called at the safepoint.  print_loader_data_graph really misses CLDG_lock, it crashes without acquiring this lock. I've added MutexLocker for it.

For @dholmes-ora: print_jmethod_ids now renamed to print_jmethod_ids_count. In order to prevent incorrect use, I did not add an API like Method::get_jmethod_ids_count. Method:: print_jmethod_ids should be enough at present.

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PR: https://git.openjdk.java.net/jdk/pull/3323