Thread Local Handshake in JVMTI functions

[David Holmes]

Hi Yasumasa,

On 31/03/2020 8:06 pm, Yasumasa Suenaga wrote:
> Hi all,
> 
> Many JVMTI functions uses VM Operation to get information. However some 
> of them need to stop only one thread - they don't need to stop all threads.
> So I think we can use Thread Local Handshake as this webrev. It is 
> example for GetOneCurrentContendedMonitor().

True, but at the moment handshakes involve the VMThread. There is work 
being done to support direct thread-to-thread handshakes and once that 
is done this kind of conversion should be more easily done. It might be 
worth waiting for that.

>    http://cr.openjdk.java.net/~ysuenaga/jvmti-thread-local-handshake/

An observation, it seems to me that calling_thread is not used when this 
is not a VMOperation.

Cheers,
David

> Also I think we can replace following VM Operations to Thread Local 
> Handshake:
> 
> class VM_GetCurrentLocation
> class VM_EnterInterpOnlyMode
> class VM_UpdateForPopTopFrame
> class VM_SetFramePop
> class VM_GetOwnedMonitorInfo
> class VM_GetCurrentContendedMonitor
> class VM_GetFrameCount
> class VM_GetFrameLocation
> 
> What do you think?
> It it is acceptable, I will file it to JBS and send review request.
> 
> 
> Thanks,
> 
> Yasumasa