dfet: setup complete: rings armed by REAL et_newbuf_hdr/et_newbuf_cluster (2 x 512 mbufs), serializer ready
dfet: S4: arming REAL et_tick via callout_reset(sc_tick, 1, et_tick, sc) (production arms at hz via et_init:1121)
dfet: S4: REAL et_tick is INPROG and parked on our serializer (lwkt_serialize_enter, if_et.c:2070) after 14 ms
dfet: S4: dispatching REAL et_stop(); its first action is SYNCHRONOUS callout_stop (if_et.c:555; _callout_cancel_or_stop sync=1 ssleep "costp" kern_timeout.c:920) which waits for the parked tick; the tick waits for our serializer; the tick would also re-arm UNCONDITIONALLY before exiting (if_et.c:2080)
dfet: *** S4: IF THIS IS THE LAST dfet LINE, THE AB-BA DEADLOCK (DF-4057) IS PROVEN IN THE PRODUCTION HANDLERS ***