RFR: 8257831: Suspend with handshakes [v4]

[Serguei Spitsyn]

On Thu, 8 Apr 2021 16:09:52 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 six commits:
>> 
>>  - White space fixes
>>  - Merge branch 'master' into SuspendInHandshake
>>  - Review fixes
>>  - Merge branch 'master' into SuspendInHandshake
>>  - Merge branch 'master' into SuspendInHandshake
>>  - 8257831: Suspend with handshake (review baseline)
>
> Hi Robbin,
> 
> thanks for the update. This is almost ready to be pushed from my pov.
> 
> Richard.

Hi Robbin,
Just a couple of comments below.

src/hotspot/share/runtime/handshake.hpp
154   // This flag is true while there is async handshake (trap)
155   // on queue. Since we do only need one, we can reuse it if
156   // thread thread gets suspended again (after a resume)
157   // and have not yet processed it.
158   bool _async_suspend_handshake;
A couple of nits above:
  L156: "thread thread" => "thread"
  L157: "and have not yet processed it." => "and we have not yet processed it."

src/hotspot/share/runtime/handshake.cpp
658 bool HandshakeState::suspend_with_handshake() {
 . . .
684   ThreadSuspensionHandshake* ts = new ThreadSuspensionHandshake();
685   Handshake::execute(ts, _handshakee);

I wonder why ThreadSuspensionHandshake is not stack allocated as SuspendThreadHandshake below:
701 bool HandshakeState::suspend() {
702   SuspendThreadHandshake st;
703   Handshake::execute(&st, _handshakee);

Thanks,
Serguei

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