8288592: JFR: Thread checkpoint no longer enforce mutual exclusion post Loom integration

[mgronlun]

Greetings,

Before integrating Loom and Virtual Threads, threads writing checkpoint meta-information claimed a checkpoint buffer from a list categorized as thread-local.
Buffers on this list are not reset eagerly as part of a flushpoint but only as part of chunk rotation, where the JFR Recorder Thread has exclusive access by issuing a prior epoch shift.

With Loom, the thread-local buffers are exclusively dedicated to meta-information for Virtual Threads.
The meta-information about the JVM thread, for example, the carrier thread, is written to a buffer located on the list categorized as global. Buffers on this list are reset eagerly during flushpoints. Before Loom, an invariant for this global list was that only the JFR Recorder Thread used it.
This invariant no longer holds. The JFR Recorder Thread will reset buffers on this list without protection and can do so in the middle of another thread's attempted writes. Some consequences are asserts in debug builds and data loss in product builds.

Some mutex mechanism for the buffers on the global list must be re-introduced to prevent the JFR Recorder Thread from resetting buffers currently in use. This change set adds back proper protection.

Testing: jdk_jfr, stress

Thanks
Markus

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Integration blocker

 ⚠️ Title mismatch between PR and JBS for issue JDK-8288592

Issue

• JDK-8288592: JVMTI GetClassSignature/getclsig005 failed "assert(_adapter.pos() == this->start_pos()) failed: invariant" ⚠️ Title mismatch between PR and JBS. ⚠️ Issue is not open.

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk19 pull/108/head:pull/108
$ git checkout pull/108

Update a local copy of the PR:
$ git checkout pull/108
$ git pull https://git.openjdk.org/jdk19 pull/108/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 108

View PR using the GUI difftool:
$ git pr show -t 108

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk19/pull/108.diff

[bridgekeeper]

👋 Welcome back mgronlun! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@mgronlun The following label will be automatically applied to this pull request:

• hotspot-jfr

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 00: Full (cfb84055)