panic: DI already started in pmap_delayed_invl_started

[Ryan Stone]

I updated my system to r254461 on Thursday, and got this panic overnight.
I have a full core and debug symbols if anybody wants me to look at
something.

panic: DI already started
cpuid = 10
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
0xfffffe1838bbc380
vpanic() at vpanic+0x182/frame 0xfffffe1838bbc400
kassert_panic() at kassert_panic+0x126/frame 0xfffffe1838bbc470
pmap_delayed_invl_started() at pmap_delayed_invl_started+0xe1/frame
0xfffffe1838bbc490
pmap_advise() at pmap_advise+0x31/frame 0xfffffe1838bbc540
vm_fault_dontneed() at vm_fault_dontneed+0x12f/frame 0xfffffe1838bbc590
vm_fault_hold() at vm_fault_hold+0x919/frame 0xfffffe1838bbc6a0
vm_fault() at vm_fault+0x78/frame 0xfffffe1838bbc6e0
vm_run() at vm_run+0x5b5/frame 0xfffffe1838bbc880
vmmdev_ioctl() at vmmdev_ioctl+0x8c2/frame 0xfffffe1838bbc940
devfs_ioctl_f() at devfs_ioctl_f+0x156/frame 0xfffffe1838bbc9a0
kern_ioctl() at kern_ioctl+0x246/frame 0xfffffe1838bbca00
sys_ioctl() at sys_ioctl+0x171/frame 0xfffffe1838bbcae0
amd64_syscall() at amd64_syscall+0x2db/frame 0xfffffe1838bbcbf0
Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe1838bbcbf0
--- syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x800ff60fa, rsp =
0x7fffdedf4e28, rbp = 0x7fffdedf4ee0 ---