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Plan: Measure Mode Repair

Overview

Restore make run-measure proof emission. The build is broken on main because the thread-lifecycle measure-mode child exits before its park-path proof line:

[thread-lifecycle] park path avg cycles:

REVIEW_FINDINGS.md and WORKPLAN.md both flag this as a blocker for relying on measure-mode closeout evidence. This is a small targeted track that should not block the Device Driver Foundation milestone but should be landed before the next selected scheduler milestone.

The repair is scoped to whatever change is actually needed in the thread-lifecycle measure-mode binary plus minimal kernel measure.rs adjustments. Do not expand the scope into a broader scheduler refactor; those follow-ups stay in docs/backlog/scheduler-evolution.md.

Conflict Surface

Owned by this plan:

  • demos/thread-lifecycle/ (the measure-mode child)
  • kernel/src/measure.rs (only narrow adjustments needed for the proof line; do not introduce new counters)
  • Makefile run-measure recipe
  • system-measure.cue if and only if the manifest must change to keep the child alive past the park path

Do not touch from this plan:

  • Other demos/* crates
  • Kernel scheduler core (kernel/src/sched.rs, kernel/src/cap/endpoint.rs)
  • tools/remote-session-client/, kernel device code, or CUE defaults

Validation Commands

  • make fmt-check
  • cargo build --features qemu,measure
  • cargo test-lib
  • cargo build-demos-capos
  • make run-measure

Success Criteria

make run-measure exits cleanly with the [thread-lifecycle] park path avg cycles: proof line emitted, the benchmark counters from kernel/src/measure.rs are unchanged or strictly expanded, and REVIEW_FINDINGS.md plus WORKPLAN.md are updated to record the closure.

Task 1: Reproduce the broken proof emission

  • Run make run-measure on the current branch base, capture the QEMU console log, and confirm the missing [thread-lifecycle] park path avg cycles: line.
  • Identify whether the child exits before reaching the park path, whether the park path runs but the proof line is suppressed, or whether the kernel measure counter is consumed before the line is printed.
  • Record the failure mode in the task branch handoff so the fix is narrowly scoped.

Task 2: Implement the narrow fix

  • Apply the minimum change in demos/thread-lifecycle/ (or kernel/src/measure.rs if the failure mode requires it) so the proof line emits before the child exits.
  • Keep counter shapes stable. If a counter must change, update the make run-measure parser and any host test that consumes it in the same task branch.
  • Avoid introducing new measure-mode entry points; this is a regression repair.

Task 3: Refresh closeout evidence and unblock dependents

  • Verify make run-measure is green and capture the proof line in the task branch handoff.
  • Remove the broken-on-main caveat from WORKPLAN.md and the paired note in REVIEW_FINDINGS.md.
  • Add a docs/changelog.md entry referencing the repair commit and note the measure-mode closeout availability for the next selected scheduler milestone.