RFR: 8223312: Utilize handshakes instead of is_thread_fully_suspended

[Robbin Ehn]

On Tue, 20 Oct 2020 02:14:56 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> The main point of this change-set is to make it easier to implement S/R on top of handshakes.
>> Which is a prerequisite for removing _suspend_flag (which duplicates the handshake functionality).
>> But we also remove some complicated S/R methods.
>> 
>> We basically just put in everything in the handshake closure, so the diff just looks much worse than what it is.
>> 
>> TraceSuspendDebugBits have an ifdef, but in both cases it now just returns.
>> But I was unsure if I should remove now or when is_ext_suspend_completed() is removed.
>> 
>> Passes multiple t1-5 runs, locally it passes many jck:vm/nsk_jvmti/nsk_jdi/jdk-jdi runs.
>
> src/hotspot/share/runtime/thread.cpp line 579:
> 
>> 577:     // That trace is very chatty.
>> 578:     return;
>> 579: #else
> 
> Without the !is_wait check none of the code below line 583 is reachable now. I would remove this now.

Since only the destructor contains any actual functionality, which is now unreachable, should I remove the entire
TraceSuspendDebugBits?

-------------

PR: https://git.openjdk.java.net/jdk/pull/729