Fix: drain SUB workers during scheduler test teardown

[puddingfjz]

Summary

• Drain both registered SUB mock workers before stopping the scheduler in
  GroupSchedulerFixture.
• Extend the teardown regression test to leave an in-flight SUB group alongside
  running and queued NEXT_LEVEL work.

Why

GroupSchedulerFixture registers sub_worker_a and sub_worker_b, but its
teardown previously drained only the NEXT_LEVEL workers. Scheduler::stop()
waits for WorkerManager::any_busy(), which includes SUB workers, so an
unfinished SUB dispatch could hang fixture teardown.

This is a follow-up to #1611 and addresses:
#1611 (comment)

Testing

• Before the fix, the extended teardown test timed out after 5 seconds.
• TearDownDrainsCurrentAndQueuedDispatches: 100 iterations passed.
• Full test_scheduler: 62 tests passed.
• All 76 non-hardware CTest entries passed; 75 ran inside the sandbox, and
  test_remote_endpoint passed when rerun outside because socket creation is
  restricted inside the Codex sandbox.
• clang-format --dry-run --Werror passed.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 51c96094-f164-47f2-9dbc-e88a2b437341

📥 Commits

Reviewing files that changed from the base of the PR and between b5261a7 and c2fbce1.

📒 Files selected for processing (1)

• tests/ut/cpp/hierarchical/test_scheduler.cpp

---

📝 Walkthrough

Walkthrough

The scheduler teardown fixture now drains SUB workers before shutdown. The teardown test submits a SUB group and verifies that both SUB workers run alongside NEXT_LEVEL workers.

Changes

Scheduler teardown coverage

Layer / File(s)	Summary
Drain and validate SUB workers tests/ut/cpp/hierarchical/test_scheduler.cpp	The fixture drains both SUB workers before shutdown. The teardown test covers running and queued work across NEXT_LEVEL and SUB workers.
Estimated code review effort: 1 (Trivial)	~5 minutes

Possibly related PRs

• hw-native-sys/simpler#1565: Modifies the same scheduler teardown test for group worker behavior.
• hw-native-sys/simpler#1611: Extends scheduler teardown coverage to drain SUB workers.

Poem

A rabbit checks the workers in line,
SUB hops twice; NEXT_LEVEL shines.
Running and queued tasks clear the way,
Teardown now ends a tidy day.
“All drained!” cries the bunny, “Hooray!”

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: draining SUB workers during scheduler test teardown.
Description check	✅ Passed	The description directly explains the teardown fix, the regression test extension, the failure mode, and the reported test results.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}