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TSan embed row counts only trace.c races and warms up on the main thread — first-use init races are invisible

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
c, shell

Research direction

Start with tests/test_tsan.sh and the embed_concurrent row, then trace the eigs_open and eigs_eval_string calls used by the reproducer. Update the TSan check to cover reports beyond src/trace.c while keeping suppressions explicit, and run the first-use concurrent states without main-thread warm-up. Done means a planted lazy-table race makes the row fail, with calibration recorded in the PR.

Written by the indexing model from the issue text.

Description

area:concurrency area:gates found-by:critic kind:gate-defect

Found by the blind critic on PR #1332 (#1275 batch B). The PR introduced a lexer data race: first-use initialisation of the operator filter tables. CI's TSan lane did not see it, for two reasons.

  • The embed_concurrent row in tests/test_tsan.sh counts only reports whose stack is in src/trace.c, so a race anywhere else in the runtime passes.
  • Its main thread lexes before any worker does, so first-use initialisation always completes single-threaded.

The critic's reproducer races it in 5 of 10 runs (and 0 of 13 on main): two threads each call eigs_open, wait on a barrier, then eigs_eval_string.

Done when

  • The TSan embed row fails on ANY ThreadSanitizer report, not only src/trace.c ones. Existing suppressions stay explicit and carry reasons.
  • A row runs two or more states that lex, compile and eval for the FIRST time concurrently (barrier-released, no main-thread warm-up).
  • Calibrated once: a planted first-use init race (a lazily filled static table) makes the row red. Recorded in the PR.
Dominant language
C
Stars
3
Forks
7
Avg merge
3h 56m
Merged PRs (30d)
102

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