8365976: G1: Full gc should mark nmethods on stack

[rm-gh-8]

Backporting JDK-8365976: G1: Full gc should mark nmethods on stack.

This PR fixes a regression introduced by JDK-8360540 where full GC stopped marking nmethods on the stack, potentially causing premature code eviction. The fix moves nmethod arming to occur after nmethod registration during full GC, ensuring that nmethods remaining after collection are properly armed and protected from inappropriate eviction.

This depends on #140

This backport has internal demand.

Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

make test TEST=test/hotspot/jtreg/vmTestbase/gc

Results attached:

linux-aarch64-specific-test.log
linux-x64-specific-test.log
macos-aarch64-specific-test.log
windows-x64-specific-test.log

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8365976 needs maintainer approval

Integration blocker

 ⚠️ Dependency #140 must be integrated first

Issue

• JDK-8365976: G1: Full gc should mark nmethods on stack (Bug - P4 - Requested)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/142/head:pull/142
$ git checkout pull/142

Update a local copy of the PR:
$ git checkout pull/142
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/142/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 142

View PR using the GUI difftool:
$ git pr show -t 142

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/142.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back rm-gh-8! A progress list of the required criteria for merging this PR into pr/140 will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 00: Full (81f75d0f)

[rm-gh-8]

/approval request for backport of JDK-8365976: G1: Full gc should mark nmethods on stack.

The change restores the correct timing relationship between nmethod registration and arming that was disrupted by JDK-8360540.

This backport has internal demand.

Low-medium risk - Addresses specific regression with well-understood root cause, but any changes to GC could introduce subtle race conditions.

[openjdk]

@rm-gh-8
8365976: The approval request has been created successfully.