--- Building fixed ng_h4.ko module (with spinlock fix applied) ---
cd /usr/src/sys/netgraph7/bluetooth/drivers/h4 && make

cc -O2 -pipe ... -Werror -DKLD_MODULE ... -c ng_h4.c
cc -Wl,--build-id=sha1 -nostdlib -Wl,--hash-style=sysv -r -Wl,-d -o ng_h4.ko ng_h4.o

BUILD=0
-rw-r--r-- 1 root 1000 22424 ng_h4.ko   (was 19432 before fix — spinlock code added)

--- Module loads successfully ---
kldload ng_h4.ko: OK (kldstat shows 3000 size vs 2000 before fix)

--- PoC run on fixed module: 30s, 1.37M data + 1.36M RESETs, no panic, guest stays up ---
(pty-based PoC doesn't exercise the l_start race path; expected no panic)