[jdk21u-dev] RFR: 8365893: test/jdk/java/lang/Thread/virtual/JfrEvents.java failing intermittently [v7]

[SendaoYan]

> Hi all,
> 
> This pull request contains a backport of commit [58e75815](https://github.com/openjdk/jdk/commit/58e7581527208dfd6dd694793e4790dcad8fc3ef) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository. I add `--enable-preview` paramerer to `@compile` and `@run junit` since unnamed is preview feature in jdk21u. All other parts are backport cleanly.
> 
> The test is changed to use Thread::join so it waits for the 100 threads to terminate, avoid the fragile sleep.
> 
> Change has been verified locally on linux-x64. Test-fix only, no risk.
> 
> Thanks!

SendaoYan has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:

 - Merge branch 'openjdk:master' into backport-sendaoYan-58e75815-master
 - Add --enable-preview to enable unnamed syntax
 - Merge branch 'openjdk:master' into backport-sendaoYan-58e75815-master
 - Merge branch 'openjdk:master' into backport-sendaoYan-58e75815-master
 - Merge branch 'openjdk:master' into backport-sendaoYan-58e75815-master
 - Merge branch 'openjdk:master' into backport-sendaoYan-58e75815-master
 - Backport 58e7581527208dfd6dd694793e4790dcad8fc3ef

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

Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/2122/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/2122/files/218ba38a..25d5be14

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2122&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2122&range=05-06

  Stats: 12618 lines in 257 files changed: 6294 ins; 4093 del; 2231 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2122.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2122/head:pull/2122

PR: https://git.openjdk.org/jdk21u-dev/pull/2122