RFR: 8307153: JVMTI GetThreadState on carrier should return STATE_WAITING

[Alan Bateman]

On Sat, 3 Jun 2023 10:53:04 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

> When a virtual thread is mounted, the carrier thread should be reported as "waiting" until the virtual thread unmounts. Right now, GetThreadState reports a state based the JavaThread status when it should return JVMTI_THREAD_STATE_WAITING | JVMTI_THREAD_STATE_WAITING_INDEFINITELY.
> The fix adds:
>  - a special case for passive carrier threads
>  - necessary test coverage to the existing JVMTI test: `serviceability/jvmti/vthread/ThreadStateTest`.
> 
> Testing:
>    - tested with the updated test: `serviceability/jvmti/vthread/ThreadStateTest`
>    - submitted mach5 tiers 1-5
>    - TBD: to submit mach5 tier 6

src/hotspot/share/prims/jvmtiEnvBase.cpp line 764:

> 762: 
> 763:   if (is_passive_carrier_thread(jt, thread_oop)) {
> 764:     state |= (JVMTI_THREAD_STATE_WAITING | JVMTI_THREAD_STATE_WAITING_INDEFINITELY);

This is testing if the jt is carrying thread_oop and it's okay for the JVMTI state to reported as WAITING when waiting for something other than Object.wait.

One thing that is a bit confusing is the function name "is_passive_carrier_thread". A platform thread is either a carrier or not. Maybe for a different PR but I think is_passive_carrier_thread should be renamed to avoid the use of the word "passive".

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PR Review Comment: https://git.openjdk.org/jdk/pull/14298#discussion_r1216368303