RFR: 8308000: add PopFrame support for virtual threads

[Serguei Spitsyn]

On Tue, 16 May 2023 22:18:17 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 1896:
> 
>> 1894:     }
>> 1895:   } else {
>> 1896:     if (java_thread != current_thread && !java_thread->is_suspended() &&
> 
> This branch checks the state when the thread is platform OR current, that logic seems a little bit messy. Would not be better to clearly separate virtual and platform threads verification? (Also, it is unclear,  we need to check platform threads here now).
> Might be some comments are needed?

You are right, thanks. Fixed now.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14002#discussion_r1196185744