`batch_manager::set_unknown()` in the parallel SMT tactic changed
`m_state` to `is_unknown` but never notified backbone workers or the
core-minimizer worker waiting on `m_bb_cv` / `m_core_min_cv`. Those
threads blocked indefinitely, deadlocking `solve()` at `t.join()`.
### Root cause
```
(declare-fun a (Int) Bool)
(declare-fun b (Int) Bool)
(assert (distinct a b))
(check-sat-using psmt)
```
Every CDCL worker returns `l_undef` with reason `(incomplete (theory
array))`. The first worker calls `set_unknown()` (a soft verdict — other
workers may still find sat/unsat) and exits. Other CDCL workers exit
when `get_cube()` checks `m_state != is_running`. Meanwhile, backbone
workers and the core minimizer are already blocked in
`wait_for_backbone_job()` / `wait_for_core_min_job()`, both of which
condition-wait on CVs that `set_unknown()` never signals. Their
predicates check `m_state != is_running`, but a CV predicate only
re-evaluates on notification or spurious wakeup.
### Fix
- **`src/solver/parallel_tactical.cpp`** — `set_unknown()` now calls
`m_bb_cv.notify_all()` and `m_core_min_cv.notify_all()` after setting
the terminal state, so waiting helper threads observe the change and
exit via the existing `m_state != is_running` guard in their wait
predicates.
### Test
- **`src/test/psmt.cpp`** — new regression covering SAT, UNSAT, and the
theory-incomplete (deadlock) path using `(as-array f)` terms to
reproduce the exact array-theory incompleteness that triggers
`set_unknown()`.
---------
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
