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

[Serguei Spitsyn]

On Fri, 21 Apr 2023 06:26:33 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> 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 1200:
> 
>> 1198:     }
>> 1199:     if (java_thread == nullptr) { // unmounted virtual thread
>> 1200:       return JVMTI_ERROR_OPAQUE_FRAME;
> 
> Where is the check for "suspended at an event" that otherwise results in `JVMTI_ERROR_OPAQUE_FRAME`?

The JVMTI `StopThread` spec has this description:
> The StopThread function may be used to send an asynchronous
> exception to a virtual thread when it is suspended at an event.
> An implementation may support sending an asynchronous exception
> to a suspended virtual thread in other cases.
> . . .
> JVMTI_ERROR_OPAQUE_FRAME:
> The thread is a suspended virtual thread and the implementation 
> was unable to throw an asynchronous exception from this frame.

This update supports all suspended mounted cases of virtual threads and returns OPAQUE_FRAME only if the target virtual thread is suspended and unmounted.
But we avoid using the mount/unmount terms in the JVMTI spec.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13546#discussion_r1173451827