RFR: 8292375: Convert ProtectionDomainCacheTable to ResourceHashtable [v4]

[Coleen Phillimore]

On Tue, 30 Aug 2022 18:20:26 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   David's comments
>
> src/hotspot/share/classfile/protectionDomainCache.cpp line 162:
> 
>> 160:   // Purge any deleted entries outside of the SystemDictionary_lock.
>> 161:   purge_deleted_entries();
>> 162:   int oops_removed = purge_entries_from_table(); // reacquires SD lock
> 
> It's confusing to have two similarly named functions (purge_deleted_entries and purge_entries_from_table). Maybe the two functions should be combined into a single `purge()`  function that performs the two steps?

I'll put purge_entries_from_table back in the mainline of this function where it used to be. I'd separated it because it was long.  purge_deleted_entries should be its own function because it goes to a safepoint so it's special.

> src/hotspot/share/classfile/protectionDomainCache.hpp line 35:
> 
>> 33: // The amount of different protection domains used is typically magnitudes smaller
>> 34: // than the number of system dictionary entries (loaded classes).
>> 35: class ProtectionDomainCacheTable : public AllStatic {
> 
> How about adding a comment to say what this table maps from/to? Something like:
> 
> // The ProtectionDomainCacheTable maps all java.security.ProtectionDomain objects that are
> // registered by DictionaryEntry::add_protection_domain() to a unique WeakHandle.

Okay, I added your comment.

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PR: https://git.openjdk.org/jdk/pull/10043