RFR: 8257831: Suspend with handshakes [v2]

[Richard Reingruber]

On Tue, 30 Mar 2021 09:33:19 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> Robbin Ehn has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
>> 
>>  - Merge branch 'master' into SuspendInHandshake
>>  - 8257831: Suspend with handshake (review baseline)
>
> src/hotspot/share/runtime/handshake.cpp line 617:
> 
>> 615:     {
>> 616:       MutexLocker ml(&_lock, Mutex::_no_safepoint_check_flag);
>> 617:       if (!is_suspend_requested()) {
> 
> The current thread is _thread_in_vm. Can it be suspended then? For a suspend it has to be in a safe thread state which it cannot leave while suspended. So it must have reached _thread_in_vm not suspended and it cannot be suspended while in that state.

Shouldn't `is_suspend_requested()` be replaced with `is_suspended()`? See also comment on declaration of `_suspend_requested`.

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PR: https://git.openjdk.java.net/jdk/pull/3191