db> bt
Tracing pid 12 tid 100024 td 0xfffff800037cd000
cpustop_handler() at cpustop_handler+0x2d/frame 0xffffffff81efc9c0
ipi_nmi_handler() at ipi_nmi_handler+0x40/frame 0xffffffff81efc9e0
trap() at trap+0x46/frame 0xffffffff81efcaf0
nmi_calltrap() at nmi_calltrap+0x8/frame 0xffffffff81efcaf0
--- trap 0x13, rip = 0xffffffff811996f0, rsp = 0xfffffe0073ddb630, rbp = 0xfffffe0073ddb690 ---
smp_targeted_tlb_shootdown() at smp_targeted_tlb_shootdown+0x320/frame 0xfffffe0073ddb690
pmap_invalidate_range() at pmap_invalidate_range+0x25c/frame 0xfffffe0073ddb720
pmap_remove_ptes() at pmap_remove_ptes+0x6d/frame 0xfffffe0073ddb780
pmap_remove() at pmap_remove+0x37d/frame 0xfffffe0073ddb810
_kmem_unback() at _kmem_unback+0x33/frame 0xfffffe0073ddb860
kmem_free() at kmem_free+0x2d/frame 0xfffffe0073ddb880
uma_large_free() at uma_large_free+0x16/frame 0xfffffe0073ddb8a0
free() at free+0x6c/frame 0xfffffe0073ddb8e0
uma_timeout() at uma_timeout+0x375/frame 0xfffffe0073ddb940
softclock_call_cc() at softclock_call_cc+0x14c/frame 0xfffffe0073ddb9f0
softclock() at softclock+0x79/frame 0xfffffe0073ddba10
ithread_loop() at ithread_loop+0x1d4/frame 0xfffffe0073ddba70
fork_exit() at fork_exit+0x83/frame 0xfffffe0073ddbab0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe0073ddbab0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---