RFR: 8249004: Reduce ThreadsListHandle overhead in relation to direct handshakes [v6]

[Coleen Phillimore]

On Fri, 15 Oct 2021 06:45:02 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8249004.cr1.patch
>
> src/hotspot/share/runtime/thread.cpp line 1771:
> 
>> 1769:   guarantee(Thread::is_JavaThread_protected_by_my_ThreadsList(this),
>> 1770:             "missing ThreadsListHandle in calling context.");
>> 1771:   if (is_exiting()) {
> 
> This seems an unrelated change in behaviour ??

So suspend_thread and resume thread's caller already takes a ThreadsListHandle so this is unnecessary and never happens.

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PR: https://git.openjdk.java.net/jdk/pull/4677