RFR: 8308000: add PopFrame support for virtual threads

[Serguei Spitsyn]

On Tue, 16 May 2023 22:04:26 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> This enhancement adds `PopFrame` support for virtual threads. The spec defines minimal support that the JVMTI `PopFrame` can be used for a virtual thread suspended an an event. 
>> Actually, the `PopFrame` can supports suspended and mounted virtual threads. 
>> 
>> CSR (approved): https://bugs.openjdk.org/browse/JDK-8308001: add PopFrame support for virtual threads
>> 
>> Testing:
>> New test was developed: `serviceability/vthread/PopFrameTest`.
>> Submitted mach5 tiers 1-6 are good.
>> TBD: rerun mach5 tiers 1-6 at the end of review again if necessary.
>
> src/hotspot/share/prims/jvmtiEnv.cpp line 1886:
> 
>> 1884:   jvmtiError err = get_threadOop_and_JavaThread(tlh.list(), thread, &java_thread, &thread_obj);
>> 1885: 
>> 1886:   bool is_virtual = thread_obj != nullptr && thread_obj->is_a(vmClasses::BaseVirtualThread_klass());
> 
> I think it would be better to check 'err' and try to handle the error before using java_thread and thread_obj.

Thanks for the comment.
It impacts the error reporting precedence which can break expectations from some tests.
But I agree, it look more natural here to check the error first.
Updated. Let's see if the all test runs are still okay.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14002#discussion_r1196147657