Fix startup deadlock with virtual threads

[amarziali]

What Does This Do

Tracer 1.67.0 can deadlock when the first untraced virtual thread loads VirtualThreadState inside mount(). The JVM’s instrumentation class-loading hook waits for mount transitions to finish, including the transition making that call.

Here we preload VirtualThreadState before installing the instrumentation. Add a fresh-process smoke test that starts a virtual thread without an active trace context.

Motivation

Additional Notes

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Jira ticket: [PROJ-IDENT]

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-08T09:56:31.993960Z	6ca119b	PR opened
🔒 Security Review	✅ Completed 2026-10-08T09:57:13.897249Z	6ca119b	PR opened

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[mcculls]

LGTM, thanks for the regression test

[datadog-official]

More details

VirtualThreadState is initialized before transformer installation, avoiding its first load during a virtual-thread mount transition. The fresh-process smoke test covers untraced virtual-thread startup with a bounded completion timeout.

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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.99 s	14.01 s	[-0.7%; +0.4%] (no difference)
startup:insecure-bank:tracing:Agent	12.98 s	13.07 s	[-1.4%; +0.0%] (no difference)
startup:petclinic:appsec:Agent	17.14 s	17.65 s	[-7.2%; +1.4%] (no difference)
startup:petclinic:iast:Agent	17.39 s	17.50 s	[-1.3%; +0.1%] (no difference)
startup:petclinic:profiling:Agent	17.36 s	17.39 s	[-1.4%; +1.2%] (no difference)
startup:petclinic:sca:Agent	17.15 s	17.62 s	[-8.1%; +2.7%] (unstable)
startup:petclinic:tracing:Agent	16.65 s	16.74 s	[-1.4%; +0.4%] (no difference)

Commit: 6ca119b9 · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.

[dd-octo-sts]

/merge

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-10-08 10:40:08 UTC ℹ️ Start processing command /merge

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2026-10-08 10:40:12 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in master is approximately 1h (p90).

---

2026-10-08 12:03:01 UTC ❌ MergeQueue: The build pipeline failed for this merge request

Build pipeline has failing jobs for d78cc03:

• oci-internal-test-publish: [${CI_COMMIT_SHA}]
• oci-internal-test-publish: [pipeline-${CI_PIPELINE_ID}]

⚠️ Do NOT retry failed jobs directly (why?).

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