8242427: JVMTI frame pop operations should use Thread-Local Handshakes

[Reingruber, Richard]

Hi Yasumasa,

Could you explain a little bit the motivation to replace these vm operations with handshakes?
Would be good, if you could add the goals as well to the JBS item.

Thanks, Richard.

-----Original Message-----
From: serviceability-dev <serviceability-dev-retn at openjdk.java.net> On Behalf Of Yasumasa Suenaga
Sent: Montag, 24. August 2020 04:40
To: serviceability-dev <serviceability-dev at openjdk.java.net>
Subject: 8242427: JVMTI frame pop operations should use Thread-Local Handshakes

Hi all,

I want to hear your opinions about the change for JDK-8242427.

I'm trying to migrate following operations to direct handshake.

     - VM_UpdateForPopTopFrame
     - VM_SetFramePop
     - VM_GetCurrentLocation

Some operations (VM_GetCurrentLocation and EnterInterpOnlyModeClosure) might be called at safepoint, so I want to use JavaThread::active_handshaker() in production VM to detect the process is in direct handshake or not.

However this function is available in debug VM only, so I want to hear the reason why it is for debug VM only, and there are no problem to use it in production VM. Of course another solutions are welcome.

webrev is here. It passed jtreg tests (vmTestbase/nsk/{jdi,jdwp,jvmti} serviceability/{jdwp,jvmti})
   http://cr.openjdk.java.net/~ysuenaga/JDK-8242427/proposal/


Thanks,

Yasumasa