RFR: 8330303: Crash: assert(_target_jt == nullptr || _target_jt->vthread() == target_h()) failed [v3]

[Serguei Spitsyn]

> This is a simple fix of three similar asserts.
> The `_target_jt->jvmti_vthread()` has to be used instead of `_target_jt->vthread()`. 
> The `_target_jt->vthread()` can be outdated in some specific contexts as shown in the `hs_err` stack trace.
> 
> I've seen similar issue and already fixed it in this fragment of code:
> 
> class GetCurrentLocationClosure : public JvmtiUnitedHandshakeClosure {
>   . . .
>   void do_vthread(Handle target_h) {
>     assert(_target_jt == nullptr || !_target_jt->is_exiting(), "sanity check");
>     // use jvmti_vthread() as vthread() can be outdated
>     assert(_target_jt == nullptr || _target_jt->jvmti_vthread() == target_h(), "sanity check");
>     . . .
> 
> The issue above was fixed by replacing `_target_jt->vthread()` with `_target_jt->jvmti_vthread()`.
> 
> There are three places which need to be fixed the same way:
>  - `GetSingleStackTraceClosure::do_vthread(Handle target_h)`
>  - `SetForceEarlyReturn::do_vthread(Handle target_h)`
>  - `UpdateForPopTopFrameClosure::do_vthread(Handle target_h)`
> 
> Testing:
>  - Run mach5 tiers 1-6

Serguei Spitsyn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - “Merge”
 - review: updated same clarifying comment in several spots
 - add comments explaining that the vthread() can return outdated oop
 - 8330303: Crash: assert(_target_jt == nullptr || _target_jt->vthread() == target_h()) failed

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18806/files
  - new: https://git.openjdk.org/jdk/pull/18806/files/6ac3b54f..c5ad80d0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18806&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18806&range=01-02

  Stats: 52905 lines in 671 files changed: 26069 ins; 23980 del; 2856 mod
  Patch: https://git.openjdk.org/jdk/pull/18806.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18806/head:pull/18806

PR: https://git.openjdk.org/jdk/pull/18806