panic: Lock filedesc structure not share locked

Hi,

with head as of r252381 on amd64, I got the following panic after
starting tmux and creating a 2nd terminal window inside tmux
(ctrl-<tmux_command_character> + c):
---snip---
panic: Lock filedesc structure not share locked _at_ /space/system/usr_src/sys/kern/kern_descrip.c:3448

cpuid = 2
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xffffff839ee566d0
kdb_backtrace() at kdb_backtrace+0x39/frame 0xffffff839ee56780
vpanic() at vpanic+0x126/frame 0xffffff839ee567c0
panic() at panic+0x43/frame 0xffffff839ee56820
_sx_assert() at _sx_assert+0x134/frame 0xffffff839ee56830
_sx_sunlock() at _sx_sunlock+0x46/frame 0xffffff839ee56860
kern_proc_filedesc_out() at kern_proc_filedesc_out+0x420/frame 0xffffff839ee568e0
sysctl_kern_proc_filedesc() at sysctl_kern_proc_filedesc+0x66/frame 0xffffff839ee56950
sysctl_root() at sysctl_root+0x1bd/frame 0xffffff839ee569a0
userland_sysctl() at userland_sysctl+0x192/frame 0xffffff839ee56a40
sys___sysctl() at sys___sysctl+0x74/frame 0xffffff839ee56af0
amd64_syscall() at amd64_syscall+0x23c/frame 0xffffff839ee56bf0
Xfast_syscall() at Xfast_syscall+0xfb/frame 0xffffff839ee56bf0
---snip---

Full textdump output available at
  http://www.leidinger.net/test/textdump.tar.2

Bye,
Alexander.

-- 
http://www.Leidinger.net    Alexander _at_ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org       netchild _at_ FreeBSD.org  : PGP ID = 72077137