RFR: 8257831: Suspend with handshakes [v2]

[Daniel D.Daugherty]

On Wed, 31 Mar 2021 03:47:28 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 two commits:
>> 
>>  - Merge branch 'master' into SuspendInHandshake
>>  - 8257831: Suspend with handshake (review baseline)
>
> src/hotspot/share/prims/jvmtiEnv.cpp line 946:
> 
>> 944: // java_thread - pre-checked
>> 945: jvmtiError
>> 946: JvmtiEnv::SuspendThread(JavaThread* java_thread) {
> 
> The comment above this still states:
> 
> // Threads_lock NOT held, java_thread not protected by lock
> 
> but the java_thread is protected by a TLH so we should document that so we know it is always safe to refer to java_thread below.

These `Threads_lock NOT held ...` comments in JVM/TI are a left over
issue from the Thread-SMR project and I think I forgot to file a follow-up
bug to clean those up.

I recommend handling that in a general cleanup issue for all of these
comments in JVM/TI (and possibly elsewhere). Please let me know if I
should go ahead and file that bug.

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