RFR: 8339725: Concurrent GC crashed due to GetMethodDeclaringClass [v3]

[Liang Mao]

> Hi,
> 
> It's a fix for 8339725. I think getting the oop from Klass::java_mirror() should use a ON_PHANTOM_OOP_REF decorator here which could make sure the oop would be kept alive in concurrent marking and return nullptr while in concurrent reference processing and unloading.
> 
> test/hotspot/jtreg/runtime and gc are clean.
> 
> Thanks,
> Liang

Liang Mao has updated the pull request incrementally with one additional commit since the last revision:

  Keep klass_holder alive and add the test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20907/files
  - new: https://git.openjdk.org/jdk/pull/20907/files/da942579..751c29bb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20907&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20907&range=01-02

  Stats: 238 lines in 8 files changed: 231 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20907.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20907/head:pull/20907

PR: https://git.openjdk.org/jdk/pull/20907