panic: Lock PFil shared rmlock not read locked _at_ /usr/src/sys/net/pfil.c:116 prior to r326363

I'm seeing this repeatedly in the last ~ 2 weeks,  present in r326363
and typically panics 1-15m post boot since this weekend's update.  I'm
currently bisecting my way back; it looks like its not in r325755, but I
can't be sure for a few more hours.

https://s3.amazonaws.com/uploads.hipchat.com/8784/2508819/MGim1y8pQt1o1xK/IMG_2698.JPG

# uname -a
FreeBSD wintermute.skunkwerks.at 12.0-CURRENT FreeBSD 12.0-CURRENT #2
r326363+fcb3a5a8a12d(master): Wed Nov 29 11:37:17 UTC 2017    
root_at_wintermute:/usr/obj/usr/src/amd64.amd64/sys/GENERIC  amd64

# dmesg

https://gist.github.com/dch/68dd6f8d44dd76c558908e71dc3e1f87#file-dmesg-log
+ other logs in same gist

Suggestions how to get from X to debugger would help, as would setting
up serial console over ipmi - this is a supermicro motherboard.

A+
Dave