RFR: 8306034: add support of virtual threads to JVMTI StopThread [v2]

[Alan Bateman]

On Thu, 20 Apr 2023 16:40:48 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:
> 
>   addressed review comments on new test

src/hotspot/share/prims/jvmtiEnv.cpp line 1197:

> 1195:   if (is_virtual && !is_JavaThread_current(java_thread, thread_oop)) {
> 1196:     if (!JvmtiVTSuspender::is_vthread_suspended(thread_oop)) {
> 1197:       return JVMTI_ERROR_THREAD_NOT_SUSPENDED;

Does JvmtiVTSuspender::is_vthread_suspended work for the alternative virtual thread implementation (-XX:+VMContinuations)?

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PR Review Comment: https://git.openjdk.org/jdk/pull/13546#discussion_r1172941986