# DF-2787 — VERDICT

status: reproduced | reproduced: 1 | impact: none | confidence: certain

Confirmed both by reading and mechanically: mtx_notlocked_ex (sys/sys/mutex2.h:436-442) documents 'Return TRUE (non-zero) if the mutex is not locked exclusively' but returns (mtx_lock & MTX_EXCLUSIVE) != 0 - TRUE when it IS exclusively locked. Harness T13 on the stock guest: while exclusively locked the function returned 1 (doc says 0); after unlock it returned 0 (doc says 1) - the exact inversion. Zero in-tree callers (rg: only the definition), so latent API trap only. On the fix kernel T13 returns 0 then 1 per the documented contract.

## Baseline vs fix kernel
baseline: baseline: 1 then 0 (inverted) | fix: 0 then 1
fix:      behavior changed as designed (see verdict)