RFR: 8373485: JFR Crash during sampling: assert(jt->has_last_Java_frame()) failed: invariant [v2]

[Markus Grönlund]

> Greetings,
> 
> When sampling threads in state _thread_in_native, there is a missing memory barrier when UseSystemMemoryBarrier is used, because it must be emitted manually.
> 
> Testing: jdk_jfr
> 
> Thanks
> Markus
> 
> PS "threads_lock" local variable was renamed to "lock" not to confuse with the global Threads_lock.

Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision:

  explicit fences

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29155/files
  - new: https://git.openjdk.org/jdk/pull/29155/files/9b8ed440..8e951ac8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29155&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29155&range=00-01

  Stats: 5 lines in 1 file changed: 2 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29155.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29155/head:pull/29155

PR: https://git.openjdk.org/jdk/pull/29155