[jdk11u-dev] RFR: 8276125: RunThese24H.java SIGSEGV in JfrThreadGroup::thread_group_id [v3]

[Jiawei Tang]

> It isn't a clean backport for two reasons.
> 1. jdk11 cannot use nullptr, so it should use NULL instead.
> 2. `parent_thread_group_handle != NULL` will cause a compile error without a type cast. 
> 
> This backport prevents a JFR operation from accessing an illegal address which has not be filled before the initialization of a JavaThread, which is created from a JNI interface.
> 
> The risk is very low since it only adds a null pointer check. Besides, This backport has be accepted in [jdk17-dev](https://github.com/openjdk/jdk17u-dev/pull/2179).  
> 
> Additional testing:
> - [x] Linux aarch64 server fastdebug, test/jdk/jdk/jfr passed

Jiawei Tang has updated the pull request incrementally with one additional commit since the last revision:

  Update full name

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Changes:
  - all: https://git.openjdk.org/jdk11u-dev/pull/2501/files
  - new: https://git.openjdk.org/jdk11u-dev/pull/2501/files/a929af31..e720c8a6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2501&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2501&range=01-02

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2501.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2501/head:pull/2501

PR: https://git.openjdk.org/jdk11u-dev/pull/2501