CAS: gc scheduler stop join race

[k-morozov]

Details

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Fixed races in the CAS GC scheduler lifecycle and made SYSTEM CAS GC START recover safely from worker scheduling failures.

Documentation entry for user-facing changes

...

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Regression jobs to run:

• Fast suites (mostly <1h)
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[k-morozov]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-08T10:24:14.279889Z	0e85e88	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Bravo.

Reviewed commit: 0e85e88b51

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[github-actions]

Workflow [PR], commit [0e85e88]

[ilejn]

@k-morozov , could you describe a scenario that requires this hardening?
May be we have an issue and/or a stacktrace?
Or a particular item in mounts-and-lifecycle.md?
Hm ... actually it is CasGcScheduler::stop joins the worker threads outside the mutex that guards them (2031-triage CAS-050) {#gc-scheduler-stop-join-race}

[k-morozov]

@k-morozov , could you describe a scenario that requires this hardening? May be we have an issue and/or a stacktrace? Or a particular item in mounts-and-lifecycle.md? Hm ... actually it is CasGcScheduler::stop joins the worker threads outside the mutex that guards them (2031-triage CAS-050) {#gc-scheduler-stop-join-race}

Not quite. Start and stop have a guard on the level above in current design. Data race related with requestRoundSoon (checking joinable without lock).