panic: mtx_lock() of spin mutex (null) @ /syzkaller/managers/i386/kernel/sys/modules/tcp/rack/../../../netinet/tcp_stacks/rack.c:16472
cpuid = 0
time = 1623957945
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe00516fd560
vpanic() at vpanic+0x1cc/frame 0xfffffe00516fd5c0
panic() at panic+0x43/frame 0xfffffe00516fd620
__mtx_lock_flags() at __mtx_lock_flags+0x1d7/frame 0xfffffe00516fd680
rack_output() at rack_output+0x1ed7/frame 0xfffffe00516fd9c0
tcp_hpts_thread() at tcp_hpts_thread+0xe50/frame 0xfffffe00516fdb10
ithread_loop() at ithread_loop+0x33f/frame 0xfffffe00516fdbb0
fork_exit() at fork_exit+0xb3/frame 0xfffffe00516fdbf0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00516fdbf0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
KDB: enter: panic
[ thread pid 12 tid 100084 ]
Stopped at      kdb_enter+0x67: movq    $0,0x164017e(%rip)
db> 
db> set $lines = 0
db>