RFR: 8259242: Remove ProtectionDomainSet_lock [v4]

[David Holmes]

On Fri, 9 Apr 2021 12:06:38 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This change makes the DictionaryEntry pd_set reads lock free, because when I set a low SafepointTimeout on the findDeadlock test, these threads were waiting on the ProtectionDomainSet_lock.  This lock is a singleton that's taken for every dictionary entry.
>> 
>> I don't know if this change will make the test never timeout again, because removing this lock caused us to hit a low SafepointTimeout on another _no_safepoint_check lock that is not so easy to eradictate.
>> 
>> Tested with tiers 1-3.  There's a test that exercises this code in runtime/Dictionary/ProtectionDomainCacheTest.java.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add overall comment and assert in count function.

Updates look good - thanks Coleen!

David

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Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3362