RFR: 8285794: AsyncGetCallTrace might acquire a lock via JavaThread::thread_from_jni_environment [v4]

[Johannes Bechberger]

> Calling JavaThread::thread_from_jni_environment for a terminated thread in AsyncGetCallTrace might cause the acquisition of a lock, making AsyncGetCallTrace non-signal-safe. 
> 
> AsyncGetCallTrace can only be called for the current threads (there are asserts for that), therefore using JavaThread::current directly and checking the termination status is semantically equivalent.

Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:

  Merge cast into condition

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8446/files
  - new: https://git.openjdk.java.net/jdk/pull/8446/files/e77e4665..8d4b60eb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8446&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8446&range=02-03

  Stats: 4 lines in 1 file changed: 1 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8446.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8446/head:pull/8446

PR: https://git.openjdk.java.net/jdk/pull/8446