=== DF-3239 decisive run (stock kernel #0) ===
cmd: cc -O2 -Wall -o df3239_pfd_exit_race df3239_pfd_exit_race.c && timeout 360 ./df3239_pfd_exit_race
rounds: 0k..508k monotonic (~1400 rounds/s, 360s wall)
output tail: [rounds:506k] [rounds:507k] [rounds:508k]  EXIT=0
guest: up throughout; no panic; no dmesg anomalies.
(508k round-marker stream omitted for size; tail preserved in task transcript)