RFR: 8308000: add PopFrame support for virtual threads

[Serguei Spitsyn]

On Tue, 16 May 2023 23:42:52 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.
>
> test/hotspot/jtreg/serviceability/jvmti/vthread/PopFrameTest/PopFrameTest.java line 127:
> 
>> 125:             resumeThread(testTaskThread);
>> 126:             testTask.clearDoLoop();
>> 127:             testTask.sleep(5);
> 
> Why sleep is needed here?

It is to better sync the output between the main and target threads.
It becomes better ordered and understandable.

> test/hotspot/jtreg/serviceability/jvmti/vthread/PopFrameTest/PopFrameTest.java line 154:
> 
>> 152:             ensureAtBreakpoint();
>> 153:             notifyAtBreakpoint();
>> 154:             testTask.sleep(5);
> 
> Why sleep is needed here?

The same answer as above.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14002#discussion_r1196134809
PR Review Comment: https://git.openjdk.org/jdk/pull/14002#discussion_r1196135294