[jdk17] RFR: 8267952: async logging supports to dynamically change tags and decorators [v2]

[Xin Liu]

> This patch fixed intermittent crashes of gtest/AsyncLogGtest.java. The root cause 
> is that previous flush() can't guarantee flush all pending messages in AsyncLog
> buffer. This patch implements flush() using a synchronizaton token and waits for
> completion. This approach isn't MT-safe but it can serialize all flush() calls in
> a thread. 
> 
> Two concurrent tests are appended to cover the hazard cases.
> This patch also comments LogConfiguration::configure_output() MT-safety.

Xin Liu has updated the pull request incrementally with one additional commit since the last revision:

  Update comments according to reviewers's feedback.

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

Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/130/files
  - new: https://git.openjdk.java.net/jdk17/pull/130/files/6f15a895..b35073f7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=130&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=130&range=00-01

  Stats: 28 lines in 3 files changed: 3 ins; 5 del; 20 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/130.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/130/head:pull/130

PR: https://git.openjdk.java.net/jdk17/pull/130