RFR: 8311177: Switching to interpreter only mode in carrier thread can lead to crashes [v2]

[Serguei Spitsyn]

> Please, review the following `interp-only` issue related to carrier threads.
> There are 3 problems fixed here:
>  - The  `EnterInterpOnlyModeClosure::do_threads` is taking the `JvmtiThreadState` with the `jt->jvmti_thread_state()` which is incorrect when we have a deal with a carrier thread. The target state is known at the point when the `HandshakeClosure` is set, so the fix is to pass it as a constructor parameter.
>  - The `state->is_pending_interp_only_mode())` was processed at mounts only but it has to be processed for unmounts as well. 
>  - The test `test/hotspot/jtreg/serviceability/jvmti/vthread/MethodExitTest/libMethodExitTest.cpp` has a wrong assumption that there can't be `MethodExit` event on the carrier thread when the function `breakpoint_hit1` is being executed. However, it can happen if the virtual thread gets unmounted.
>  
>  The fix also includes new test case `vthread/CarrierThreadEventNotification` developed by Patricio.
>  
>  Testing:
>  - Ran new test case locally
>  - Ran mach5 tiers 1-6

Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:

  review: addressed nits in new test

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/19438/files
  - new: https://git.openjdk.org/jdk/pull/19438/files/a0f5d278..2f75975f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19438&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19438&range=00-01

  Stats: 18 lines in 2 files changed: 0 ins; 2 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/19438.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19438/head:pull/19438

PR: https://git.openjdk.org/jdk/pull/19438