Thread Local Handshake in JVMTI functions

[Yasumasa Suenaga]

Hi,

JDK-8240918 has been pushed, so I made a patch for GetCurrentContendedMonitor(). How about this?

   http://cr.openjdk.java.net/~ysuenaga/jvmti-thread-local-handshake/2/

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

calling_thread is used for creating JNI reference:

```
*monitor_ptr = jni_reference(calling_thread, hobj);
```


If it is ok, I will make patches for other JVMTI functions.
However the patch might be bigger, so I want to separate as below. What do you think?
(I think we can file them as subtask under JDK-8201641)


* Monitor operation
     - VM_GetOwnedMonitorInfo
     - VM_GetCurrentContendedMonitor

* Frame operation
     - VM_UpdateForPopTopFrame
     - VM_SetFramePop

* Thread operation
     - VM_GetFrameCount
     - VM_GetFrameLocation
     - VM_GetThreadListStackTraces
     - VM_GetCurrentLocation
     - VM_EnterInterpOnlyMode


Thanks,

Yasumasa


On 2020/04/01 21:29, Yasumasa Suenaga wrote:
> Thanks David!
> 
> If JDK-8201641 is not assigned when JDK-8240918 is resolved, I will start to work for JDK-8201641.
> (It would be large patch...)
> 
> 
> Cheers,
> 
> Yasumasa
> 
> 
> On 2020/04/01 19:05, David Holmes wrote:
>> On 1/04/2020 11:02 am, Yasumasa Suenaga wrote:
>>> Thanks Dan and Serguei!
>>>
>>> I added a comment for this to JDK-8201641.
>>>
>>> David, can you share Bug ID for thread-to-thread handshake?
>>> I want to record it to JDK-8201641 as a blocker.
>>
>> https://bugs.openjdk.java.net/browse/JDK-8240918
>>
>> I heard the RFR could be as soon as tomorrow :)
>>
>> Cheers,
>> David
>>
>>>
>>> Yasumasa
>>>
>>>
>>> On 2020/04/01 1:59, serguei.spitsyn at oracle.com wrote:
>>>> Hi Yasumasa,
>>>>
>>>> Yes, this works needs to be done.
>>>> I'll take look at you webrev.
>>>>
>>>> Thanks,
>>>> Serguei
>>>>
>>>> On 3/31/20 07:41, Daniel D. Daugherty wrote:
>>>>> Add Robbin to this thread...
>>>>>
>>>>>
>>>>> This reminded of the following RFE that Robbin filed:
>>>>>
>>>>>     JDK-8201641 JVMTI: GetThreadListStackTraces should use Thread-Local Handshakes
>>>>>     https://bugs.openjdk.java.net/browse/JDK-8201641
>>>>>
>>>>> We could update 8201641 to include everything that Yasumasa-san is requesting.
>>>>> Would be a good place to track it...
>>>>>
>>>>> Dan
>>>>>
>>>>>
>>>>> On 3/31/20 7:40 AM, Yasumasa Suenaga wrote:
>>>>>> Hi David,
>>>>>>
>>>>>> On 2020/03/31 19:16, David Holmes wrote:
>>>>>>> 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.
>>>>>>
>>>>>> Thanks, I will be back to this topic when thread-to-thread handshake is done.
>>>>>> I wondered at first why VMThread involves handshake. Its improvement is welcome for me ;)
>>>>>>
>>>>>>
>>>>>> Cheers,
>>>>>>
>>>>>> Yasumasa
>>>>>>
>>>>>>
>>>>>>>> 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
>>>>>
>>>>