RFR: 8257831: Suspend with handshakes [v3]

[Richard Reingruber]

On Wed, 31 Mar 2021 06:42:27 GMT, David Holmes <dholmes 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 three commits:
>> 
>>  - Merge branch 'master' into SuspendInHandshake
>>  - Merge branch 'master' into SuspendInHandshake
>>  - 8257831: Suspend with handshake (review baseline)
>
> src/hotspot/share/runtime/thread.cpp line 2105:
> 
>> 2103:     if (is_external_suspend()) {
>> 2104:       java_suspend_self();
>> 2105:     }
> 
> It is not at all clear to me how this method should interact with thread suspension ??

In JavaThread::wait_for_object_deoptimization() the current thread can transition to the safe state _thread_blocked. In that state it can be suspended. In the baseline version wait_for_object_deoptimization() checks for suspension explicitly and self suspends if positive. With this enhancement it happens implicitly by calling SafepointMechanism::process_if_requested().

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