Panic after update from r297313 -> r297348

[David Wolfskill]

Unfortunately, the serial console only seemed to be echoing characters
in quasi-random spurts, yielding such things as:

...
r() at lcpu_initcpu_initclocks_bsp+0x37f/frame 0xffffffff820dbb40
initclocks() at initclocks+0x20/frame 0xffffffff820dbb50
mi_start+0x2c

Tracing  td 0xffc_et_start+0x2d9/frame 0xffffffff820dbaa0
loadtimer() at lrame 0xf configtsp() at clocks_bsp+0x37f/frame 0xffffffff820dbb40
initclocks() at initclocks+0x20/
Tracing pid 0 tid 100000 td 0xffffffff81d11200
lapic_et_start()c_et_start+0x2d9/frame 0xffffffff820dbaa0
+0x2cimeoadtimer+0x102/frame 0xf20dbac0
db> 
pid 0 tid 100000 td 0xffffffff81d11200
lapic_et_start() at lapic_et_start+0x2d9xffffffff820dbaa0
loadtimer() at loadtimer+0x102/frame 0xffffffff8imer+0x239/frame 0xffffffff820dbb10
cpu_initsp() at f820dbb7pid 0 ti td 0xffffffff81_start()c_et_staf820dbaa0
r() at loadtimer+0x102/ffffffff8
                                configtimer() atcpu_initxfffffffpid 0 tif820dbaa0| |___ _ __ ___  ___ | |_) | (___ | |  |   ___| '__/ _ \/ _ \|  _ < \___ \| |  | |dtimer() at loadtimer+0x102/frame 0xffffffff8 0xffffffff820dbb10
c| |   | | |  __/  __/| |_) |____) | |__| |
b| |   | |  \___|\|200
configtimer() at configtimer+0x239/frame 0xffffffff820dbb10
cpu_initclocks_bcpu_initsp+0x37f/frame 0f820dbb40
initclocks() at initclocks+0x20/frame 0x820dbb50
mi_startup() at mi_startup+0x118/frame 0
Tracing d 100000lapic_et_start() at lapic_et_start+0x2d9sp+0x37f+0x2c
db> 0
 0xffffffff820dbsp+0x37ff820dbb4ks() at 
mi_startup() at up+0x118/frame 0xffffffff820dbb70
btext() at btext+0x2c
db> bd 100000+0x102/frame 0xfcpu_initframe 0xffffffff+0x2c
pic    [K]ernel (1 of 2)
r|m 6.bConfigure Boot [O]ptions...
 H| vpanic+0x182/frame 0xffffffff820db4a0+
db_commaf0                                        .--         
sp+0x37f0/frame 0xffffffff820db6kdb_trapf820d        .---.....----.______               ____   _____ _____   ____|             |  _ \ / ____|  __ \ 
bte                                       
Uptime: 1s                                                                     -c0+0x4db8+0x15eef8+0x8+0x]+-y+:.                  `:`


at which point I had already (semi-blindly) tried "panic", so I
tried "reset", then I was able to escape to the loader, unload the
new kernel, boot the previous one, move the various kernel*
difrectories around in /boot, then reboot again to old kernel:

FreeBSD freebeast.catwhisker.org 11.0-CURRENT FreeBSD 11.0-CURRENT #2028  r297313M/297313:1100104: Sun Mar 27 06:27:24 PDT 2016     root at freebeast.catwhisker.org:/common/S4/obj/usr/src/sys/GENERIC  amd64

I'm still building on my laptop; while I hope I don't have the character-
dropping issues there (as I have no serial console on it), I also don't
have much of a way to communicate what it displays if it (also) panics.

Apparently my attempt at "panic" didn't get a crash dump.. :-(

Any suggestions for diagnosing this?

Peace,
david
-- 
David H. Wolfskill				david at catwhisker.org
Those who would murder in the name of God or prophet are blasphemous cowards.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 603 bytes
Desc: not available
URL: <http://lists.freebsd.org/pipermail/freebsd-current/attachments/20160328/b1f99ef0/attachment.sig>