RFR: 8306034: add support of virtual threads to JVMTI StopThread [v6]

[Alan Bateman]

On Thu, 27 Apr 2023 09:14:29 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> This enhancement adds support of virtual threads to the JVMTI `StopThread` function.
>> In preview releases before this enhancement the StopThread returned the JVMTI_ERROR_UNSUPPORTED_OPERATION error code for virtual threads.
>> 
>> The `StopThread` supports sending an asynchronous exception to a virtual thread only if it is current or suspended at mounted state. For instance, a virtual thread can be suspended at a JVMTI event. If the virtual thread is not suspended and is not current then the `JVMTI_ERROR_THREAD_NOT_SUSPENDED` error code is returned. If the virtual thread was suspended at unmounted state then the `JVMTI_ERROR_OPAQUE_FRAME` error code is returned.
>> 
>> The `StopThread` has the following description for `JVMTI_ERROR_OPAQUE_FRAME` error code:
>>> The thread is a suspended virtual thread and the implementation 
>>> was unable to throw an asynchronous exception from this frame.
>> 
>> A couple of the `serviceability/jvmti/vthread` tests has been updated to adopt to new `StopThread` behavior.
>> 
>> The CSR is: https://bugs.openjdk.org/browse/JDK-8306434
>> 
>> Testing:
>> The mach5 tears 1-6 are in progress.
>> Preliminary test runs were good in general.
>> The JDB test `vmTestbase/nsk/jdb/kill/kill001/kill001.java` has been problem-listed and will be fixed by the corresponding debugger enhancement which is going to adopt JDWP/JDI specs to new behavior of the JVMTI `StopThread` related to virtual threads.
>> 
>> Also, two JCK JVMTI tests are failing in the tier-6 :
>>> vm/jvmti/StopThread/stop001/stop00103/stop00103.html
>>> vm/jvmti/StopThread/stop001/stop00103/stop00103a.html
>> 
>> These two tests will be excluded from the test runs by the JCK team and then adjusted to new `StopThread` behavior.
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   install_async_exception: set interrupt status for platform threads only

src/hotspot/share/prims/jvmti.xml line 11984:

> 11982:     <errorid id="JVMTI_ERROR_OPAQUE_FRAME" num="32">
> 11983:       Information about the frame is not available (e.g. for native frames),
> 11984:       or the frame is not suitable for the requested operation.

After re-reading the spec changes, I'm wondering if we can improve on "or the frame is not suitable for the requested operation".  StopThread doesn't have a frame parameter. ForceEarlyReturn doesn't have a frame parameter either as it's implicit (the current frame). I wonder if wording something like this might be better:
"or a function on a thread cannot be performed at the thread's current frame".

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PR Review Comment: https://git.openjdk.org/jdk/pull/13546#discussion_r1178984510